I have encountered the author of Tehillim referred to directly as David HaMelekh. However, on no small number of occasions, I've also encountered the author of Tehillim referred to as "The Psalmist" ...
When one says Tehilim there is a Yehi Ratzon which is published at the end which says "to be said after saying Tehilim". Who authored this Yehi Ratzon?
Who is the accepted author of Psalm 137, and if it was David Hamelech, then is it accepted as a prophecy?