Output not defined

[jonas.thornvall at gmail.com]

Can any web programmer tell me why output is not defined?
I know this is python group but my code is so rudimentary that probably any sufficient good webprogrammer can figure it out, but i am lost."I've tried comp.lang.javascript"

Problem is I've looked upon this for a week or two, and i just can't figure out why output is not defined. 

My hangup is probably because it works without problem when i run it in under windows XP browser, and that make me confused."I started program it in XP but now i want to transition into more modern browsers, Linux and windows 10" 

https://3d16zci4vuzyxt8hxvovrg-on.drv.tw/Website/midi.html 

Any help or even suggestion would be greatly appreciated.