Is it possible to export multiple audioclips into one single wave file?

Here is the problem: I have several audio clips(like the music single track, one do the piano, one do the base, and one do the drum), and if player choose some instruments, like piano , base and drum, I should combine all these clips together and give player a wav file which contains all the clips he selects, I know how to deal with only one audio clip, but has no clue on multiple clips. Can anyone help, thanks!