Korgy, your problem can be solved by simply create an existing style and edit the tracks (drums, accomp). Just choose any style you want, hit 'record' button, and then choose 'current style'. Now you're in style editing menu. Here you can edit the style's variation/fillins/intro...for example, choose V1 (stands for variation 1) to edit its tracks.

Hit the 'trk.select' button to assign the instruments of your choice. Say you want to replace a piano with a electric piano, choose the track, hit the 'E.piano' and choose the instrument. Now hit the 'exit' button to bring you back to the previous page. Hit the 'trk.select button' again to go back to the style editing menu. Finally, hit record to save the edited style to any location you want. This is all in PA80's manual (9b-1). If you don't have it, you can download it from http://www.korgpa80.com/pa80/en/main.html

You can change the volume of your tracks in Mixer: Volume, page 1 of Song Edit Menu.

Mikey