I'm composing a traditional four-part part-writing piece with a soprano, alto, tenor and bass. The song progresses from a F Major chord to an A Major chord. In the former chord, the bass is on C, and in the latter, I want to move the bass up to C#.
My question is, would such a move be allowable (assuming no issues arose with the other voices)? I know certain movements aren't allowed, but couldn't find any information on the augmented unison interval in particular.