There are some singer/songwriters whose songs and style are so dependent on the personality, identity, musical style, etc. that they really can't be performed by anyone else. I think some of Bill Morrissey's songs are like this. (Note this is MY opinion, not necessarily that of anyone else, although my late husband Curmudgeon also felt that way.)

If the songs can only be sung by the writer, they will die.

Linn