Hello. Here is the complete program, just unzip it all to the same folder and run ./rat.sh for Linux; if you're not running Linux, either run rationale.py with the argument smfcsoundtest.rat, or run rationale.py and hit Ctl-O to open smfcsoundtest.rat. If you move the mouse while it's playing, especially after the higher instruments start, it skips constantly. If you uncomment all the lines in rationale.py under where it says "comment next line to worsen csound performance", it is maybe a little better, but it doesn't seem like a solution, and it's not 100% better. Sorry I couldn't get a more isolated example put together, it didn't have the same problem when I just asked it to play a simple csd file and bound mouse movement to a print function. Obviously it's trying to do to much, but can anyone point me in the right direction for forcing it to do Csound stuff before the GUI? Will this require the user to set rt priority? Thanks for any advice. -Chuckk -- http://www.badmuthahubbard.com