Multi-track recording software -- or sequencing software -- replicates the tools and functions of a professional recording studio on a home computer. It's called a sequencer because the software records a time-stamped sequence of MIDI events and plays them back in the same exact order [source: The Java Tutorial].
For a simple MIDI recording setup, all you need is a MIDI synthesizer or controller connected to a computer, plus some kind of sequencer software. The standard MIDI connector is the five-pin MIDI DIN that attaches to the joystick port of a PC soundcard. Or you can invest in a small MIDI USB or Firewire adapter that easily plugs into the USB or Firewire port of a desktop PC or laptop. For a more complicated MIDI recording setup, you might need a multi-port MIDI interface that allows you to connect several MIDI devices to a computer at the same time.
Like traditional studio recording, software sequencers record audio onto individual tracks. There's a separate track for the percussion, another for guitar, another for piano, another for vocals, and so on. Most modern sequencers can record both digital audio and MIDI data. A vocal track, for example, would be recorded with a microphone and represented in the sequencing program as sound waves. A MIDI track recorded from a keyboard would be represented as dots and bars corresponding to MIDI events.
To record a song on a sequencer, you typically lay down one track at a time. Once the percussion track is recorded, for example, you can play it back and record over it with the bass line. This is called real-time recording.
But since MIDI data is digital, it's also extremely easy to edit. The visual layout of a sequencing program is chronological, displaying recorded audio from left to right, beginning to end. You can grab chunks of audio -- say a drumbeat -- copy it and paste it 100 more times. Or you can take the entire chorus, including 16 different tracks, and drag it back 12 bars.
Most sequencing software also comes with a host of virtual knobs, faders and effects. You can adjust the volume, stereo pan and audio effects of each track to create the perfect mix. The software allows you to export your file as an MP3 or WAV and burn them onto a a CD.
Now let's talk about virtual instruments, one of the coolest advantages of making music with MIDI.