In shape-note singing, the melody line (outside of fugal sections) is usually in an inner voice, either the alto or the tenor. There is frequent part-crossing, which can make it even harder for a listener to distinguish which part is singing which note.

"Ecstasy" may not be a very "melodic" piece, but the melody is in the tenor part. One reason it comes across a bit indistinct is because the effect here is more of a chant than a song--the harmony seldom leaves the tonic chord.