My formula (inspired by DanM):
Piano recording seems to be a topic that comes up every once in a while.
This post describes my recording setup. It lists all the equipment, shows how they are connected, and it provides a recording sample to show what kind of result you can reasonably expect using this setup. My solution is a 300 USD solution in the sense that I believe all the necessary equipment can be had for a total of under 300 USD (excluding the computer). I am certain there are better solutions, I am certain there are cheaper solutions, and there are cheaper AND better solutions. But what I describe is what I know works for me, and one I feel can be easily duplicated by others.
The Big Picture[/b]:
Microphones[/b]: I use a pair of MXL-990. Most recent "sales" prices I've seen peg them at 60 USD a piece. Conventional wisdom seems to favor condensor microphones when it comes to recording piano. See links below to additional microphone discussion and recommendations. The mic stands may seem unnecessary, but I think they make positioning microphones so much easier. Get the kind with boom stick if you can. The mic stands are usually inexpensive. (IIRC, I got mine for under 20 USD each.) I usually place my microphones 2~3 feet from the curvy side of my grand piano with the lid fully open, the mics are usually about 1~2 feet higher than the soundboard. Feel free to experiment with different placements to find the mic positions that work best for your piano and your room acoustics.
Pre-Amp[/b]: I use M-Audio's AudioBuddy. It got it for about 80 USD. There are other options discussed in other threads linked below, but this one works well enough for me. If you use condensor microphones, you will need something to supply it "phantom power." The AudioBuddy does just that.
Microphone Cables[/b]: These connect the microphones to the pre-amp. Not much to talk about here... cables are cables. The connector types you need obviously depend on the microphones and the pre-amp you choose. If you use the MXL-990 and AudioBuddy like I do, then you want XLR connectors on both ends of the cables. Get cables that are long enough so you can place your computer (assuming you plan to record with your computer) far enough away from the mics so the mics won't pick up the computer's noise. (I use cables that are 25 feet long, they seem to work fine.)
A/D Converter[/b]: I use Griffin Technologies' "iMic" USB interface, can probably be had for under 40 USD these days. The A/D Converter converts analog signal from the pre-amp to digital signal that your computer records. Your sound card may already have this function (in which case you can connect the outputs of the pre-amp directly to your computer's audio input jack(s), or you can buy pre-amps that also double as an A/D Converter that provides a USB or FireWire interface to your computer.
"Y-Cable"[/b]: I use a Y-cable because the AudioBuddy pre-amp gives me two 1/4" phono output jacks while my "iMic" USB audio interface gives me only a 1/8" stereo audio input jack. The "Y-cable" is used to connect these two -- it has two male 1/4" phono connector and one male 1/8" small stereo connector. (IIRC, I got this for under 7 USD.) You won't need it if you get one of those combined "pre-amp with A/D with USB/FireWire interface" unit.
Computer and Software[/b]: Lots of choices. I happen to use an Apple PowerBook G4 ("Titanium") running Felt Tip Software's "Sound Studio" shareware. It's shareware licensing fee is pretty inexpensive (IIRC, sub-40 USD) and has a 14 day free trial period. If you use a Mac, GarageBand should work just fine. If you use Windows, the software called "Audacity" is available for free. It seems to work fine on Windows, but I wouldn't recommend it for the Mac because it's just SLOW on the Mac the last I tried it. Basic editing functionalities like cutting, pasting, fade-in, fade-out are all there... and there are other more advanced functionalities that, frankly, I have never needed to use. On the Mac, I just use iTunes to convert myh stuff to MP3. On the Windows, Audacity can do it for you (and it seems to me there are tons of Windows freeware that deals with MP3).
Recording Parameters[/b]: Your recording software would likely offer many different sampling rates and bit depths at which to record your performance. For reference, CD-quality recording has a sampling rate of 44.1 kHz (samples per second) at 16 bit. Professional studios record at 96 kHz and 24 bits or higher. As an amateur hobbyist, I'm generally happy with what I got using 44.1 kHz, 16-bit setup. There may be no point in recording at higher sampling frequency and higher bit depth for two reasons: (1) your other equipment may not be good enough to warrant the extra resolution anyway, (2) you will always have to throttle it back down to 44.1 kHz and 16 bit if you burn your music into an Audio CD, and you'll compruess away a lot of stuff if you post your recording in MP3 format anyway.
MP3 Conversion Parameters[/b]: It's basically a balance between sound quality and file size. Higher bit rate means higher audio quality and bigger file size (if the lenght of music stays constant). Lower bit rate means lower audio quality and smaller file size. If you believe the guys who brought you iTunes, you can theoretically get audio quality as good as iTunes' if you compress your music to 160 kbps using MP3. My opinion is that if you start with a good, clear recording, you can get good-sounding MP3 even with low bit rates. Otherwise, garbage in, garbage out. So don't get hung up over MP3 bit rates. Lower bit rates often means you get smaller files, and people are more likely to download if your files aren't too big as to look intimidating.
10. The Result
[/b] (2.5 minutes, 1.2 MB, right-click, "Save As...").
It's recorded using the equipment and parameters described above with me at the piano, and encoded in MP3 format at 64 kbps. It's a "raw" recording in the sense that it has not been mastered, there's no EQ tweaking applied and no artificial reverb added... it's bascially what the microphones picked up (except the little bit of fading at the beginning and the end so they don't sound abrupt). The audio is by no means professional-sounding, but there is sufficient dynamic range, you can hear phrasing, you can hear pedaling, you can hear where the articulation is good and where it is sloppy, etc. So I think it's good enough for Internet posting on a Forum like this for your peers to critique your playing. As mentioned before, there are better recording solutions, and there are cheaper recording solutions... but this is the kind of result you can reasonably expect if you record using the "recipe" presented above. (Just in case anyone is curious, the piano is a 6'6" Kawai model RX-A grand piano.)
It may be fun to read lots of discussion and do lots of research, but the most effective way to learn is to just hit the record button and start recording.
Go forth and record, have fun, good luck, and come back and share your recordings![/b]