Here is a picture, and you can see the melody voice has a rest for the last 8th note, but I also added a rest for the alto and tenor. Is this correct, or would one rest have been ok?
3 Answers
If it is important to show the individual voices, give each voice a rest. For instance, most editors would notate a Bach fugue like this:
In general keyboard writing, not strict polyphony, one rest, centred between the two voices, is fine.
If this WAS four-voice writing (with divisi alto?) and the tenor voice was tacet at this point, A would be correct, with the bass voice stems-down and a rest in the tenor. But for 'keyboard style' the bass notes should follow normal stem direction rules (B).
The less distracting and unnecessary info the better to ease the reading of the piece. The quaver rest could be moved more centrally to clarify its relavance to all three voices.
If you want to be pedantic you can write two rests. Otherwise a single rest is totally acceptable.
If the rests were of different lengths, then you'd have to put in both of them