Do you mean sampled audio? Or a chip sound effect?
Both actually are supported already.
Viewing post in MusicStudio - Music/SFX editor for Commodore 64 comments
Yes, but you will need to change the source code of the player routine. In the source file MusicPlayer2.a look for .playSFX and this block of code is active when SoundEffectsActive is defined. The variable .fxnoteDuration is used to decide how long to use the voice for sound effects before resuming the music.