I have a choir director who sometimes has us drop the final consonant in lines, because she says the sound is better. She always gets a fight from me, because I say he meaning is just as important.

I've always identified "Swing Low Sweet Chariot" with the Fisk Jubilee Singers, who made the song popular in the 19th century. Here's a 1909 recording by the Fisk Jubilee Singers that pronounces the "t," but lightly:

https://www.youtube.com/watch?v=GUvBGZnL9rE

And here's a more recent Fisk performance:

https://www.youtube.com/watch?v=QoTGtiriybg

https://en.wikipedia.org/wiki/Swing_Low%2C_Sweet_Chariot