Hello
for communication between Arduino and Flash
Beltran berrocal making some actionsript file to add in flash...Arduino code&examples - by b of Progetto25zero1
you have to use serproxy, a small xml server to translate message from serial to tcp and reverse.
serproxy can be found here -> http://webzone.k3.mah.se/projects/arduino-workshop/upload/default.asp?folder=10
on the Tom igoe pages, there is some code for an MIDI player in Wiring/Arduino
http://www.tigoe.net/pcomp/code/archives/arduino/000738.shtml
hope this help
regards
eric