Pino Donaggio was a crooner before he took to film music. The two Randy's (Newman & Edelman) started out as singer/songwriters. Danny Elfman was Oingo Boingo before Batman. Michael Kamen had his New York Rock n Roll Ensemble. Cliff Eidelman released an album full of sung songs. Did Marvin Hamlisch sing over his piano too? Who else can shout as well as shake?
Legrand used to sing a lot on tv appearances back in the 70s; you know, so he could appear on tv and play his music. Bacharach sings. Don't quit your day job, Burt.
Nico Fidenco started out as a singer before he became a rather prolific film composer.
Yes and edda's husband Giacomo wrote out all his partitures and did the orchestrations for years coz he wasnt trained. He would hum what he wanted and Giacomo wrote it up.
I can say that despite having a gift for melody, James Horner was about as bad a singer as one could imagine.
He could play piano, French Horn, various synthesizers and was good at ping-pong but from everything I've learned, the man could not sing, even a little.