Yes, it would. That’s is the only method I’ve seen used in stories for guitar playing with custom guitars/basses. You could create arm overlays and attempt to animate them but it’s a lot of work.
HOWEVER, even though there isn’t any actual prop we can add to characters or remove that are guitars/basses, there’s two that are automatically added to a character if you use any of the guitar/bass animations other than the air guitar animations. Air guitar animations are self-explanatory, basically just meant for pretending to play.
Animations with automatic props:
idle_guitar_neutral_loop
play_guitar_netrual_loop
play_guitar_energetic_loop
sing_guitar_sad_loop
sing_guitar_neutral_loop
talk_guitar_neutral_loop
idle_bass_neutral_loop
play_bass_neutral_loop
talk_bass_neutral_loop
If you don’t like either of those automatic props, then you will need to need use an overlay of your choice and manually animate it in front of your character. 