Commodore DOS, aka CBM DOS, was the disk operating system used with Commodore's 8-bit computers. Unlike most other DOS systems before or since, CBM DOS was integrated in the internal ROM of the floppy disk drives(as well as the very few hard disk models Commodore made for its 8-bit range), not loaded from disk into the computer's own RAM at startup.
Versions of CBM DOS
1.0
X.Y
2.6 – the most common version due to its use in the 1541 floppy disk drive
S.T
References
Immers, Richard; Neufeld, Gerald G. (1984). Inside Commodore DOS. The Complete Guide to the 1541 Disk Operating System. DATAMOST, Inc & Reston Publishing Company, Inc. (Prentice-Hall). ISBN 0-8359-3091-2.
My apologies to the authors who have had their articles into me on time - school is coming first for me and having to do a lot of coding for several classes was the major contributing factor to the delays.
All you would need to do to play a different music is to change the music data at the bottom, and a few lines of the code.
Both the drums and the skydive do a very fast frequency down, so it is the most significant byte of the frequency which is reduced..