To be honest, I don’t know much about recording acoustic pianos other than that it is black magic.
You need at least one microphone — two is better because that gives you stereo sound — and a recording device. Of course, you can use your computer to record on, but that does mean you need to put it somewhere near the piano (or buy very long cables).
You will get the best recordings with a set of good condenser microphones, but they are expensive and you need other equipment as well to connect this all to your computer.
Not just the quality of the microphones matters: the acoustic quality of the room is at least as important.
For good results you really need to go to a professional recording studio.
Some budget options are:
A cassette tape recorder. This is the low-budget option. The sound quality will be pretty bad, but it’s better than nothing. To put the recordings on your computer, you can connect the tape recorder from its (Head)phones Out to the computer’s Line In or Mic In.
A mobile phone or digital camera. Why not? You’ll probably have to put the phone or camera a few feet away from the piano otherwise the sound will easily be too loud for the microphone to handle, resulting in nasty clipping distortion.
An MP3 player (or MiniDisc) with recording capability. The sound quality varies from one model to the next, and you can get very acceptable results with this.
Using the built-in microphone from your laptop computer. Most laptops have a built-in microphone, but this typically isn’t a very good one. It’s intended for speech, not high fidelity sound.
Using an external microphone with your computer. There are several different types of microphones. The most common is a “dynamic microphone”. That type will work, but it’s better to use a “condenser microphone”, which is much more sensitive and therefore more suitable for picking up the wide range in dynamics that a piano can produce.
Of course, if you use just one microphone your recording will be in mono. You will need to use two microphones (or a single stereo mic) and a mixing deck to record in stereo. In addition, condenser microphones require their own power source (called “phantom power”) so it’s best to get a mixer that provides this.
An external microphone I can recommend is the Samson C01U. This is an inexpensive condensor microphone that plugs directly into your computer’s USB port, which means you don’t need any other equipment to use it and the sound quality is great.
If you use two Samson C01U mics to capture stereo sound, then you won’t need a separate mixer, just two available USB ports.
For recording, you can use the free Audacity software. If you want to work with more than one audio track at a time, I recommend REAPER. Even though Audacity can work with multiple tracks too, Reaper is a true multitrack workhorse. This powerful program is very inexpensive and you can try it out for free for an unlimited time.
Using a portable digital stereo recorder. Two popular ones are the Zoom H4 and Zoom H2, and I hear the Edirol recorders are pretty good too. These handheld devices deliver good results and are very easy to use.
After you’re done recording, you can connect them to your computer with a cable (or a memory stick) and transfer your recordings (as WAV or MP3) to your hard drive.
Some of these, such as the Zoom H4, will work with external microphones too.
For more information on recording acoustic pianos, I defer to:
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