i was always told the musky flavor or whatever ya want to call it comes from only 2 things

1) a gut shot ripping open intestine or stomach

2) when gutting to always seperate there "junk" before continuing because theres a scent gland in there that mixes with there uring so if they drip urin or you cut the gland and either spill on your meat you might as well stop cutting and throw it away right there.

now i didnt think number 2 was true i thought it was an old wifes tale till i looked it up one day and found this.

http://www.youtube.com/watch?v=WeO4ogItu7s