These databases are available on GALILEO. You will need the password to access them if you are not on the Emmanual College campus.
In addition to the databases on GALILEO, the following sites also have biographies of composers and song writers.
International Dictionary of Black Composers by 
The New Grove Dictionary of Music and Musicians by 
Baker's Biographical Dictionary of Musicians by 
The Harvard Biographical Dictionary of Music by 
The Norton-Grove Dictionary of Woman Composers by