Why do bells sound out of tune?

Рет қаралды 124,448

Күн бұрын

Bells often sound of tune, but why? Are they really out of tune? Or is something else going on? Dive into the acoustics of bells with me and we'll uncover this mystery!
0:00 Intro
0:48 Piano Harmonics
1:54 Natural Harmonic Series
3:00 Bell partials (Bell overtones)
4:37 Comparing major & minor sounds
5:42 Stacking minor thirds (diminished chord)
6:24 Conclusion
This is the first video in a series I'm planning where I dive behind the scenes of the carillon. In future videos I'm hoping to cover more on acoustics, instrument design, performance techniques, arranging and composing, practicing, instrument maintenance, and more. Let me know what you'd like to hear about in the comments below!
Incorporated carillon footage:
Bach Cello Prelude: • Bach Cello Suite No. 1...
Ode to Joy: • Ode to Joy, Beethoven ...
Asturias (Leyenda, Albeniz): • Asturias (Leyenda) by ...
Tina Turner Tribute on bells (What's Love Got to Do With It): • Tina Turner tribute on...
Acknowledgements / reference videos:
- Those out of tune bells I referenced are from Zuidhavenpoort, NL. These are actually the oldest surviving bells from a forestroke (automatic hour melody). These are 16th century van den Gheyn bells. They're out of tune, yes, but they're amazing! • Carillon Zuidhavenpoor...
- Here's an AMAZING Video comparing the harmonic series to bell partials, that dives more into the phantom fourth (related topic): • Why Composers Love Bells
- Natural Harmonic Series graphic, adapted from Christophe Dang Ngoc Chan (cdang), CC BY-SA 3.0 creativecommons.org/licenses/b..., via Wikimedia Commons
- Bell partials compared to Natural Harmonic Series graphic, adapted from John Gouwnes, Playing the Carillon, an Introductory Method
Composing for carillon? Check out my video here • Composing for Carillon... and accompanying article newmusicusa.org/nmbx/composin...
Interested in supporting the channel? Consider becoming a channel member for just a few $ a month. Check out the offer by clicking the "join" button.

Пікірлер: 716

@joeybrinkbells Ай бұрын

I had a lot of fun making this, and I have some other ideas for behind-the-scenes looks at bells/carillons. Let me know what other questions you have or what you'd like to hear about!

@michaelguccione6168 Ай бұрын

I assume you were talking about diminished scales at the end of the video. Would love to hear that on bells

@kaylamattheashames3289 Ай бұрын

I would love to see a video about alternate bell tunings! I have read about major third-tuned bells but haven’t found any recordings.

@pauljackson1638 Ай бұрын

Would love to know HOW the partials of bells are tuned. Are the forms modified and the bells recasted over and over or is the bell cast once and then milled to fine tune it?

@potatospade1217 Ай бұрын

I’m curious as to whether there’s some kind of optimal geometry involved in bell shapes. Also would love to know which music written specifically for bells or the carillon sounds the best, or least out of tune.

@marcusmicksch Ай бұрын

Does weather condition affect the tuning? For example if it is freezing cold, do the bells sound different?

@potatospade1217 Ай бұрын

For literally years it has always bugged me why bells sounded a bit off. Now I finally know why and hearing that diminished chord was an absolute joy! Thank you so much for sharing this!

@voornaam3191 Ай бұрын

Learn more about music. You could have known about these harmonics, too, if only you had searched it on KZfaq or online. No offence at all, often people got to live their life first.

@thorin1045 Ай бұрын

it also comes form the size and the fact that it is usually around stuff, so it is not as clear as a normal instrument would be. rarely you have stairs and towers in your piano.

@searchiemusic Ай бұрын

@@voornaam3191 learn more about talking to people lmao

@llamamusicchannel7688 Ай бұрын

@@voornaam3191dude literally is leaning more by watching this. You can't learn more without consuming content that teaches. You also can't learn anything before you learn it. So why hang shit on someone for learning something after you?

@rickwilliams967 17 күн бұрын

Really? You just happened to have a need for this exact explanation, yet didn't attempt to find out on your own?

@mumiemonstret Ай бұрын

Imagine an entire town listening to you demonstrating the bells to us!

@HelloKittyFanMan Ай бұрын

You can hear the carillon for several blocks around it, but it's really not loud enough for even a whole small town's worth of people to hear. I mean... unless that town really is just a few or several blocks wide in one or both dimensions.

@johnpekkala6941 Ай бұрын

The city hall where I live, Sweden - Västerås, have one of these and it plays different melodies every hour that I hear while walking around between the shops and cafees on weekend together with some of my friends. It has always been a part of this place for me.

@noahway13 Ай бұрын

Much of the world has lost a sense of community, I think bells could bring that back.

@HobbyOrganist Ай бұрын

There is a town in Tyrol Austria that has the largest outdoor pipe organ that can be heard across the town and beyond; The Heroes’ Organ (“Heldenorgel”) at Kufstein Fortress is the largest free-standing organ in the world. It was built in 1931 by organ builder Oskar Walcker in the Citizens’ Tower at Kufstein Fortress to commemorate the dead of World War I. The original organ had two manuals. Extensive alterations were made to the organ in 1971, with the addition of a third and fourth manual; the organ then had 46 stops and 4,307 pipes. In 2009, the organ was comprehensively refurbished and extended to 65 stops and 4,948 pipes. The sound created by this magnificent organ can be heard throughout the town. The organ is played daily at 12 noon to honour the war dead and to remind of peace. The play can be heard throughout the whole town and the surrounding areas.

@jookles 16 күн бұрын

@@johnpekkala6941Hey! I’m going to stockholm soon, any recommended places to visit? Thanks!

@usbcd360 Ай бұрын

After you explained the partials, I pulled out my synthesizer, built a simple patch with those specifications, and it sounded right on. I've tolled tower bells before, but never had a chance to play the carillon, so this was pretty fun.

@joeybrinkbells Ай бұрын

that's awesome!!

@antonliakhovitch8306 Ай бұрын

Man thank you so much for the idea, now I gotta try this!

@JerehmiaBoaz Ай бұрын

If your synth has a ring modulator you could try modulating your primary oscillator with a second one tuned 32 half steps down, that creates an almost perfect minor third. Ring modulation = partial creation.

@matthewiskra771 28 күн бұрын

All that music theory I learned over the years (as an amateur and insufferable pedant), nothing was about bells. Thanks for the informative video.

@yehvacat Ай бұрын

Wow, I knew bells had their unique partials but never saw anyone go in detail, so cool! I myself play frame drums that can have an open sound and a longer decay so drum partials is another interesting topic to me

@joeybrinkbells Ай бұрын

I don't know much about drum partials, but I would be interested to learn more!

@yehvacat Ай бұрын

@@joeybrinkbells Yea, I need to get into it, I tried finding some articles but I mostly find physics, it's too much for my brain. I found partials of a concert single headed tom in an article (ascending: b, [octave higher] a flat, b, e sharp, a flat, b flat...) and it looks not much like my (21" in diameter) Iranian daf frame drum. It is tuneable (mine got 14 tuning screws!), I think my tuning is quite even. I looked at it's frequencies and it goes something like (also ascending) g, f, c sharp, f sharp, b... also faint partials I ommited. Fun fact: it's possible to play drums manipulating their partials with hands on them - see: Mohammad Reza Mortazavi, he plays this Iranian drum too

@BrentBlueAllen Ай бұрын

I like how everyone in town heard this video being made

@HelloKittyFanMan Ай бұрын

Haha, most likely not everyone in the whole town, and not most of the video.

@Barnaclebeard Ай бұрын

@@HelloKittyFanMan Thank you for acknowledging the Deaf and hard of hearing. Invisible disabilities often get ignored.

@HelloKittyFanMan Ай бұрын

@@Barnaclebeard: I didn't acknowledge them specifically (as you may be able to read unless you're blind or just hard of seeing), but they would obviously be included, of course. Also, "deaf" isn't a personal or brand name.

@Barnaclebeard Ай бұрын

@@HelloKittyFanMan Hello my arrogant friend, it is nice to speak to you again. The word "deaf" with a small d is an affliction to the hearing. "Deaf" with a capital d is a culture. That is the correct spelling for Deaf culture, with a capital d. It seems you are not the fucking know-it-all that you think you are.

@randomassortmentofthings 26 күн бұрын

@@HelloKittyFanManThe Deaf community is capitalized. " Many people in the Deaf community prefer use of a lowercase “d” to refer to audiological status and the use of a capital “D” when referring to the culture and community of Deaf people. The National Association of the Deaf has not taken a definitive stand on this issue."

@Elriuhilu Ай бұрын

When you started explaining about the harmonics on the piano, I had a sudden urge to throw a bone into space in slow motion and see it turn into a spaceship.

@thomapple Ай бұрын

Either I'm missing a reference or I'm having a stroke or you're having a stroke

@Elriuhilu Ай бұрын

@@thomapple The notes he played sounded like the start of Also Sprach Zarathustra, the classical music piece used in 2001: A Space Odyssey. In the movie an ape ancestor of humans discovers he can use a bone as a club. There's a scene transition in which he throws the bone club in the air and the scene dissolves into a spaceship flying through space.

@thomapple Ай бұрын

@@Elriuhilu aah I see thanks for explaining!

@Elriuhilu Ай бұрын

@@thomapple No worries :)

@NickWeissMusic Ай бұрын

Exploiting the harmonic series was Strauss’ intention. It starts out with perfect 5ths and 4ths- very simple interactions- then ends the phrases with major and minor chords, “evolving” into more complexity.

@nicholaselder-dicker525 Ай бұрын

This is hands down the best explanation of the physics behind harmonics I have ever seen! Simple, concise, and the perfect blend of science and art. Thank you!

@justafloatingcoconut1368 Ай бұрын

Love to hear Joey spreading bell knowledge. Really well edited and well written!

@joeybrinkbells Ай бұрын

Thank you!

@InventorZahran Ай бұрын

So that's why diminished chords sound so good on bells!

@samylemzaoui2298 Ай бұрын

wow that diminished arpegio sounds so good on bells compared to piano ! i never liked bells for anything more than one to three note motifs but this really opened my mind to the possibilities that are out there

@johns7734 Ай бұрын

I used to work as a pipe organ tuner and one of the instruments that we serviced was the organ at Ocean Grove, NJ. This is in an auditorium with no heating or cooling so every time they were going to have a performance, we would have to do a quick retuning of the instrument since every time the temperature changes, it goes out of tune from the thermal expansion/contraction of the pipes. More specifically, the brass reeds would change more than the lead flue pipes. However, since it's a lot easier to retune a flue pipe and there are a lot less of them, we whould de-tune the flue pipes to match the reed pipes.

@Adreitz7 Ай бұрын

Not sure why I got recommended this, but it was interesting! I think this discussion is specific to bells with the classic bell shape, though. I grew up hearing a handbell choir in my church and I was shocked by the difference when they switched to more "modern" handbells that had a spring-mounted rubber ball that hit a metal "tongue" supported on one side. These bells, due to their simple geometry, produce a sound much closer to a pure sine wave than classical bells (or even a piano), making the tune a lot clearer and easier to hear.

@manueldeubler1127 Ай бұрын

Man, when I finally understood it I was like: 'That rings a bell'

@Barnaclebeard Ай бұрын

Banned.

@michaelberentsen6827 Ай бұрын

I'm so happy to have watched this video! For years I've wondered why church bells focused on the minor 3rd and diminished 5th. Thank you!

@LWmusik Ай бұрын

According to old world logic, church bells do in fact sound fairly satanic lol

@jonasmarucha Ай бұрын

Good afternoon, Mr Brink (It's me again). Thanks for taking the time to explain it, I like the explanation! It's pretty simple and easy to understand.

@joeybrinkbells Ай бұрын

Glad to hear!

@jonasmarucha Ай бұрын

@@joeybrinkbells Thanks. You know what I also like to hear? Your voice. No joke, it's really sooth and calming to hear you explain something.

@HobbyOrganist Ай бұрын

On top of the Metropolitan life tower in NYC is a clock and bronze bells, and they played Westminster every quarter hour, there was always one bell that sounded much louder than the other like the hammer was hitting harder. Mind you the bells were up on around the 49th floor, but they are large bells and could be heard quite a distance! My dad called me from a payphone one day, and as we talked I could hear the bells in the background, so I knew where he called from LOL! they were that loud but the one bell was considerably louder than the others. Sadly, the building was converted to condos and they permanently shut the bells off because residents didn't want to heard them.

@NikolajLepka Ай бұрын

I guess that's why church bells are used for melancholy or creepy soundscapes, because of that inherent minor sound

@sweeterthananything Ай бұрын

this is amazing info. i've messed with additive synthesis and related things for much of my life at this point, always thinking about acoustic instruments along the way, and there's still so much to grasp about them. for one the "hum tone" is a compele shock--i'd always been informed that subharmonics don't exist except electronically or as a theoretical indulgence.

@joeybrinkbells Ай бұрын

I know! The hum tone is mind-blowing! One way around this is to define the fundamental an octave lower, so the fundamental IS the hum tone. But the problem here is that the strike tone is clearly an octave higher than the hum tone, so carillons define the strike tone as the fundamental

@jcortese3300 Ай бұрын

I remember watching something -- probably on PBS or somewhere like that -- ages ago where someone had tried turning bells with a different profile that gave them that major third overtone. They looked pretty weird compared to the normal sloping profile of a regular bell, but the sound was instantly recognizable as a major sound. I don't know what happened to that project; I mean, it's not like anyone's making new carillons every week, so if there were a new bell profile, it would hardly take over the world quickly. I just wonder what the status of that project is, and whether any new bell-turning profiles have ever been used.

@joeybrinkbells Ай бұрын

Yes!! There are a couple of major-3rd bell installations in the world, notably Crystal Cathedral in California. Intereatingly, the major 3rd bell sound never really caught on; people seem to prefer minor 3rds in their bells(!), so the quest for major 3rd bells kind of fizzled out about 25 years ago.

@13_cmi Ай бұрын

@@joeybrinkbells It might be for that spooky old timey medieval feel. It could have uses but I'd imagine changing tunings between major and minor bells wouldn't work well.

@jcortese3300 Ай бұрын

@@joeybrinkbells Thanks for mentioning Crystal Cathedral; I just looked up a video on them and indeed the bells have a sort of Sutton-Hoo-helmet shape that's really interesting. I'm guessing that you'd play different pieces on a major 3rd carillon; they Harry Potter theme would probably sound great on yours, but maybe less so on that one.

@xXSocietyBlowsXx Ай бұрын

Now, I've never taken any music theory classes or physics classes for that matter but walking away from this video I don't think I have ever understood sound better. Great video, great information, and excellent delivery. Keep it up! Subscribed.

@luc8254 Ай бұрын

I'm so glad you actually played the diminished chord! Thanks mate very good! 👏👏

@DIYDSP Ай бұрын

You explain this SO WELL. And sweet playing, too.

@jean-david-ouellette Ай бұрын

Fascinating! My morning alarm is bells, so I've been wondering this for years... Awesome video!

@Hanensens Ай бұрын

Ive wondered about this for so long! Thank you!

@chrisd561 Ай бұрын

Absolutely fascinating. Thank you!

@MrDendroth Ай бұрын

Very interesting ! Your explanation is very clear ! Thanks !

@Withing_ Ай бұрын

Awesome video! Top quality and I learned something totally new!

@williampamblanco Ай бұрын

I had never stopped to think about this, super cool!

@ExAnimoPortugal Ай бұрын

Thank you for posting this. I have always wondered about it, but never provoked so much curiosity that I would search why.

@worldsheaviestjamband93 Ай бұрын

Incredible video. I was never aware of the the different harmonic overtones of bells or any other overtone series at all. Instant sub!

@mthiessen134 Ай бұрын

A master class on harmonics! Well done. At a young age I understood I enjoyed listening (as opposed to just hearing). I slowly became an audiophile. I met a man who became a good friend who taught me to listen to the space between the notes. A whole new world opened up. When we listen to understand rather than just hear, our brain connections multiply exponentially.

@mohitrahaman Ай бұрын

I was not aware about your video, but just about 2 days after the upload date of this video I was searching for bell samples for my project, it made me think about that out of tune striking sound to the in tune ringing sound and ways to simulate it. I was watching everything from church bells, gregorian ones, chinese gongs, indian temple bells and also Wintergatan's Marble Machine song played on the church bell organ which I learnt was called the carillon, and also I think I have also seen you before in a Rob Scallon video. I found your vidoe recommended today. Thanks for the upload.

@LarryMickelson Ай бұрын

This is so cool! I love how you dont shy away from showing the physics necessary to understand the message you want to share. And that you do it visually. So cool. I had forgotten about this funny feature of bells until you reminded me with this superb video!

@joeybrinkbells Ай бұрын

thank you!

@samuelharvey4925 29 күн бұрын

This is one of the best videos I've ever watched, thank you for this!

@pjotrkolster Ай бұрын

Oh wow this was really interesting to hear! I already knew that the overtones were the cause of the bells sounding 'off', but never knew what the partials themselves were. Thanks a lot for this!

@RicktheRecorder Ай бұрын

Absolutely fascinating. Thank you.

@bradjohnson9671 Ай бұрын

This was the best explanation I've ever heard. I've always been interested in bells, particularly wind bells. Always wondered why some sound so much better than others. Now I know.

@ccdipao Ай бұрын

Ive been wondering this for so long!!! Thank you for explaining this so clearly :)

@milligoree Ай бұрын

Fascinating, thank you!

@annoyedspy2173 Ай бұрын

Amazing video! This was really interesting to learn

@getoutofZEWEI Ай бұрын

Oh wow this is so interesting! I've always wondered this but I never would have guessed it was due to a different harmonic series entirely!! Thanks for sharing ❤

@CatFish107 Ай бұрын

Fascinating insights. Thank you. Without knowing any of this, I've not felt that bells were off, or out of tune, but that they had their own "flavor". Now I know a little bit more about that flavor. 😊

@elipz1337 Ай бұрын

Very instructive and well put video ! Keep it up Joey !

@joeybrinkbells Ай бұрын

thank you :-)

@bradarmstrong3952 Ай бұрын

Thanks so much for this clear and concise explanation of bell harmonics! I learned alot, and that means everything!

@ChrisThomasBone Ай бұрын

I never once thought to imagine a bell as a 3 dimensional wave function, but it makes so much sense! Fascinating video, I'm obsessed with acoustic physics

@vbertrand Ай бұрын

Thanks for that wonderful insight!

@lfakroll Ай бұрын

So glad I got this in my recommendations! This info will come in handy when synthesizing bell-like sounds.

@davemason6870 Ай бұрын

That was really cool and informative. Thanks a lot!!

@Ri-ver Ай бұрын

Another thing to consider is the Bell's geometry and how waves and fractions of waves fit into that space. The tapering that happens between the large and small radius is what leads to most of the overtones you covered

@vicomt Ай бұрын

seeing a visualisation of the wavefront would be interesting

@christianaastorp6105 Ай бұрын

Excellent explanation. A proper mix of physics and music.

@shaunhayward Ай бұрын

This is a brilliant explanation! Thank you so much! I love the science of music and this is incredibly well-explained.

@erikgruber9736 Ай бұрын

Great video, very enlightening

@ric8248 Ай бұрын

Mate this is fascinating! Great video.

@dedede5586 Ай бұрын

i always wondered this! thank you so much for this video

@HappyOrganMan Ай бұрын

Great explanations, thanks!

@mr.octopie6199 Ай бұрын

This was super interesting, thanks!

@t3hSurge Ай бұрын

You killed it. Fantastic video.

@Doeff8 Ай бұрын

This is an excellent accessibel explanation!

@kendallperry9247 Ай бұрын

Really nice job of explaining this. I'm not very good at physics, but this illustrated the phenomenon of harmonics really well.

@Ambidextroid Ай бұрын

Wow that is so interesting, I never would have thought about what a minor 3rd based overtone series would sound like

@jimmypockrus7725 Ай бұрын

Fascinating, I've always loved carillons.

@PeterJnicol Ай бұрын

Great vid. Thanks!

@burntsider8457 Ай бұрын

Interesting topic well presented. Thank you for the lesson.

@mmbcproductions3340 Ай бұрын

That was extremely interesting, well done and thank you

@MikeWalls7829 Ай бұрын

Thank you that was really interesting, I have always thought bells sound out of tune but you showed me why and how, thinking of the scales you mentioned it all makes sense 😀

@the0val Ай бұрын

Huge thanks for this explanation! I jag heard that "bells have a minor third", but hadn't really understood it or been able to hear it before this video

@Tm0g762 Ай бұрын

Very informative and enjoyable.

@zevelikon Ай бұрын

Blew my mind! You’ve got yourself a new subscriber 😊 and I would love to hear more about the physics of bells compared to other instruments

@Aaron-rh7sz Ай бұрын

This was a wonderful lesson.

@tomghzel Ай бұрын

Today I leanred something valuable. Thanks for the insight!

@AlexanderWright1 21 күн бұрын

One of my favourite things when change ringing is ringing the bells down in rounds. They get faster and faster as the period of swing decreases, with the sounds all blending together until the main sound is the hum tones, not the strike notes. When being fancy, at the very end, we miss a swing, then attempt to stop the bells still with one catch. This produces one last loud round of strike notes against the background hum. It's most beautiful to listen to, and great to perform.

@drdarwinator Ай бұрын

I think a cool thing in the future to see as a behind-the-scenes thing would be more about all the connections/cabling that go from the bells down the player’s position. Thanks for explaining why the bells may sound out of tune!

@joeybrinkbells Ай бұрын

love that idea!

@jacobsolbryds5931 Ай бұрын

Omg, i needed this video so badly. I live right next to a big church, and the bells sound so much out of tune, and I thought it was a bid silly, that they dont tune them. Now i know they dont have to! I think i will enjoy them even more now! Thank you

@julessisti Ай бұрын

Nice, thank you for this insight! love nerding abouth those things!

@memarkiam Ай бұрын

Fascinating. Thanks.

@ashtreegarden5079 Ай бұрын

this was really interesting, thank you!

@theinconsistentpark9060 Ай бұрын

I learned some thing cool today! Thanks!

@mumblbeebee6546 Ай бұрын

Thank you, that was new, interesting and well done!

@sophigenitor Ай бұрын

Awesome explanation.

@chopper3lw Ай бұрын

Wow, just wow. I'd never thought about why they sounded "off" and I never thought it'd be this interesting either. Thanks!

@campanaro_99 Ай бұрын

As a bell enthusiast i see this video as an absolute win. Finally someone explained bells VERY well, kudos to you!

@joeybrinkbells Ай бұрын

thank you! there are lots of videos out there on the harmonic series, and I could find a couple on bells and bell partials, but I thought there was a need for a video that focused solely on the minor 3rd partial because it's so important :-)

@joe8133 22 күн бұрын

Awesome video!

@morganwolf Ай бұрын

Love this, and made me think of the Carillon I got to play in college (Davis Memorial in Alfred NY) and how it was a partial step off but in tune with itself. It was very noticeable after getting used to the practice carillon we had since that was more or less on tone.

@franklindmurphy Ай бұрын

That is a very good explanation and cool video. Always knew that they sounded out of tune and it was weird. Thanks for the explanation. Very good.

@HinseMutter Ай бұрын

Thank you! Every year I get back to my sheet music and some day I will finish a piece for church bells! Really fascinating instrument to compose for. I live one street away from a carillon in the Netherlands. Hearing the programmed music every 15 minutes plus live concerts twice a week is a privilege.

@Roy_1 Ай бұрын

Great video, thank you sir!

@panosfloyd Ай бұрын

Thanks for the explanation! 🙂

@sergiohs391 Ай бұрын

GREAT video!

@georgecarlson1460 Ай бұрын

Thank you for this! It explains a lot -- whether the bell is huge and in a tower or small handbells!

@wanderfra42 Ай бұрын

Ah-a!!!!! Thanks a lot for perfectly explaining this mindboggling sensation that haunted me since today!! 😄

@kylepieczynski9576 Ай бұрын

Didn't expect to hear Asturias, nice!

@Nicenigel14 Ай бұрын

I always thought the carillon sounded off, but this video helped me to understand why they sound different and appreciate that difference instead of dislike it. Also even in isolation, the full diminished chord sounds really cool on the bells. And on top of that, the next video recommended at the end is from the Bionicle, Mask of Light movie?! Awesome

@KazeNoTaniFarmHakuba Ай бұрын

I’ve always wondered this.. Thank you.

@MinurielLai Ай бұрын

This is so cool!

@rawkhawk414 Ай бұрын

Your love for bells made my heart ring.

@fosvandermeer8470 Ай бұрын

I was checking out a video about large bells in the world and also thought to myself: these bells sound like they're in minor! This is very badass! Thank you for the explanation

@DrGroo Ай бұрын

Thanks for this. Having spent 13-or-so years listening to the carillon of the Uni I attended, it's great to finally understand the physics of that "out of tune" sound. I'm surprised it's a simple as a m3 partial.