Select your equipment, method of connection and recording software. If you are recording a piano, you will need a recording-quality microphone, a microphone cable, a microphone power source (if needed) and an adapter to connect your microphone to a computer. If you are recording a keyboard, you can use a simple "jack-to-mini-jack" cable, or you may wish to purchase a USB recording device, which is compatible with a standard instrument cable. If you are recording a keyboard, you will also need a decent pair of headphones to listen as you record. For either piano or keyboard recording, you will need a computer with an up-to-date processor and a good amount of storage space (at least 50 GB of free space). There is a number of recording software available for home musicians, each with their own advantages and disadvantages. A few well-known applications are GarageBand, Audacity, Reason, Ableton Live, and Pro Tools. Research and select a software that suits your needs.
Connect your instrument to the computer. If you are recording a piano via microphone, place the microphone stand near the piano without allowing it to touch the piano, as vibrations can effect recording. Then connect the microphone to the mic cable, connecting it to a power source if needed, then connect the output cable to a USB adapter. Some microphones do not use standard mic cables, but instead utilize 1/4" instrument cables -- in this case, connect the microphone according to the keyboard instructions. If you are connecting a keyboard, you may choose to plug directly into your computer's "Line In" jack with a jack-to-mini-jack cable. However, unless your computer has an expensive sound card, this will provide a weak and poor quality signal. You may wish to purchase a USB recording device, which plugs into the computer and accepts standard 1/4" instrument cable plugs. Once you have connected your instrument, check your computer's System Settings under the Sound option, and make sure the correct input channel is selected.
Open your recording software application. After following the documented installation and setup instructions, you should be almost ready to start recording. Make sure that the software application is reading from the correct input channel, and plug headphones into the computer's headphone jack if you wish to monitor yourself. Select any digital effects you would like to use, adjust the volume of your instrument (or the distance of your microphone) to eliminate distorted signal, and click the "Record" button. You are now ready to record music from your piano or keyboard.