this is a really really vast subject
i just wrote a response to someone else you might want to read
http://www.linuxquestions.org/questi...hreadid=249973
if you have a keyboard you can use your soundcards gameport as midi in/out
oh yea you said you have livedrive
or you can use a mouse either in a program or with a virtual keyboard
i personally like muse
check out also rosegarden
and seq24 for something more "loopy"