rosh chabura
it is just that you never find a singer that composes his own music
Abie Rotenberg composed many songs that he sang. Look at Journeys. Almost all the songs Abie sings.
Also, that is how the music industry works. Not all composers are singers. Hashem gave Boruch Levine many talents. One is to compose, one is to sing and one is to teach. Each one can work without the other. If he would not be a composer, would you say his singing is not excellent and inspiring?