Multiple MIDI instruments or playback styles on one staff?

[waterfall]

What I'd like to do is change the MIDI instrument sound on one staff within the course of the piece. I haven't been able to find if this is even possible. I'd also like to change the human playback style at a certain point in the work and this doesn't seem possible either. I hope I'm wrong, but it appears that once playback style and MIDI instrument is selected for a staff or track it remains unchanged for the course of the work.
Specifically, I'm trying to change the bass voice from voice oohs to choir aahs at one point and at another place I'd like to change from a swing playback style to a classical or none. Is this possible and if so, how?

Thank for the help!

[michelp]

It is possible using a text expression with an effect on playback. Create one, and in the thumbnail Playback, select Type->Patch change. Select you patch.
Place the expression at the appropriate place on the staff.
You may have to create a second expression to revert to the first patch.
For swing, you can use Type->swing in a similar manner.
These expressions can be made invisible, using the text style "hidden".

PS : you can also define different patches and midi channels for each layer of a specific staff in the Instrument list window. Then enter the music in the layer corresponding to the sound you need.

[waterfall]

Thanks for the clear and concise suggestions, Michel.
I will try them soon.

J.