Suggestion to change voices within a part

I work with percussion parts mostly, and often have an issue with changing voices in the middle of a piece. For example. on one piece I have been working on, the xylophone player switches to a marimba. I would like the playback to reflect the change in voice without having to create a brand new part just to listen to it for that one part, and that would be confusing if I were to give out that music. This would also work for switching between a melodic and battery style part, like often happens in percussion ensembles.