is it musically possible to modulate the vocals but not the backing track and have it sound ok, or will it always sound dissonant
if you want to raise the vocals but not the rest of the music, you would have to do it note by note. each note would move a different amount. you could just do it harmonically using mostly maj/min thirds and also 4ths, or better yet re-imagine the line entirely. but i'm not sure i understand the situation you are doing this for