You just can't sample someone else's fart if it has already been used in a track. Probably if it has a creative commons license you should be fine. But...a fart is pretty easy to make...so...why not just use your own?
On that note...
Why not just make a copyright claim to the C Major Triad? You'd get paid royalties every time it appears in a music theory textbook and in methods books. That's where my money would be! lol
I have a weak spot for that Shure SM57, btw. I like the distinctive coloration better than the more ubiquitous SM58, but they are both great mics. You can also do some cool mods on the 57. They sound really nice without the transformer, for one. You can also upgrade to a better transformer. One of the selling points of the 57 is it's one of the cheapest professional mics you can buy, and part of that is due to foreign manufacturing--and that's with the real 57s, not the Made in China copies. I think there is either an American or a German transformer currently on the market for about $75 that supposedly enhances the quality of the 57.
I've used condenser mics for a few years now and I'm sick to death of how high-maintenance they are. I've probably spent close to $500 on large and small diaphragm condenser mics and MAYBE have one or two left that still works reasonably well. There are such extremes in humidity where I live that I have no guarantee that my condensers are going to get much good use, and I can't afford to waste the money. 57s and 58s sound professional, reject background noise better than condensers, and can stand up under heavy abuse.
I do have a need for overhead mics, though, so I'm sure I'll eventually bend and get a pair of condensers strictly for that purpose. I used one of my last remaining condensers for a sampling project to use on demos and just accepted a result I wasn't entirely happy with. I tried out the 57 and was completely blown away that it outperformed the more expensive mic.
The one negative I have is something I'd probably find with any mic... There's this antique Baldwin piano I use for rehearsals about twice a week and the sound is amazing. I only did two velocities since I do have to keep in mind the voice limitations of my favorite sampler. Even after applying just enough EQ to eliminate some low-frequency rumble, I still got lower-than-expected S:N on the lower velocity group. I'm pondering whether I should just go with it or if I should try again by placing the mic closer to the middle of the piano strings to eliminate brighter harmonics, playing with a slightly higher velocity than previously used in order to get more signal. Or would I do just as well keeping what I have and hope that the lower-velocity sample will be quiet enough that the noise won't even really be noticeable? And would it be best either way to add a LPF to further cut noise, or would that make it too non-linear?
I dunno... Resampling for a lower velocity would be a difficult option since the piano is located in a room adjacent to a media/TV control room with always-on equipment. Rather than using a central cooling unit, the building cuts costs by opening the door and running a box fan, thereby ruining any realistic expectations I might have of getting good samples of that piano until probably sometime in November...