This scene is special in a way since it presents Elvis on stage accompanied by real musicians. Only very few of his movie performances featured real musicians. In fact the last one to do so was "Viva Las Vegas" five years earlier. And you'd have to go back seven years more to see him perform with Scotty Moore, Bill Black, DJ Fontana and The Jordanaires in 1957's "Loving You" and "Jailhouse Rock" respectively. In "Trouble With Girls" it's The Mellomen who act as "The Bible Singers", a part of the travelling Chautaqua troupe managed by Elvis-character Walter Hale. Elvis actually recorded a few times with the Mellomen during the 1960ies.
Apart from featuring real musicians this scene also has an almost documentary touch to it. Back in the 50ies before Elvis went to Sam Phillips' Memphis Recording Service "to make a record for my own use", as he told the audience in 1969, his dream was to join a Gospel Quartet. That's why he auditioned as bass [sic!] singer - and was rejected. The rest is history.
So, in a way this scene presents Elvis as the musician as which he probably saw himself before anything else: As singer among other singers, his voice interconnected with others. And what a great performance of a gospel classic, first recorded by him for his 1961 gospel album "His Hand in Mine" this is!