Would it be possible? Not exactly a typical sequencer, but something like this:
I would record every note on my electric and acoustic guitar, bass, drums, and piano (essentially creating samples of each instrument that I own). Then export them to .wav and organize them by folder (/data/guitar/electric/string6fret1_F.wav). Then using a picture of each instrument made in Paint or similar program, have the user click the frets, drum, or note (piano) and have it place the note onto a playlist of notes. Then, File -> Export -> MP3 or WAV would export the song to a file.
Yes I think it is possible. It woluld take a lot of disk space for each note that could be played. A long time ago in a land far away in Windows 3.1 I did something like that. I know I don't have anything of it left and if I did it would be on a 3.5 disk and I don't have a 3.5 drive anymore.
I will wrack my brain and see if I can remember what and how I did it.