A sequencer is a piece of software that records the MIDI events onto a computer and then lets you manipulate them onscreen. This is called sequencing and is one of the most popular uses of MIDI. Think of a sequencer as a tape recorder for MIDI, but unlike a tape recorder, you can have virtually unlimited tracks.

The amount of control you have while editing is unparalleled. If you're interested in recording home demos, being able to sequence a background string part, flute line, or piano line to play over is invaluable. Many professional musicians prepare fully working demos of their music this way, before presenting it to other band members. If you don't have a guitar synth, don't worry. Most sequencing programs let you enter notes into a notation window for constructing various instrumental parts; using a guitar synth or a keyboard controller is just a much faster way for note entry. Once the tracks are into the computer, you can tweak individual notes, change keys and tempos, add effects, and even fix rhythmic mistakes.

MIDI files are small and you can fit many files on your computer, even with a small hard disk. Some bands use sequenced parts live and play them through a laptop computer. The most popular sequencers are Cubase, Logic, Vision, and Cakewalk. Sequencing is a great tool because it gives you total control over the instruments and their sound. If you don't have musicians near you to play with, sequencing can be a great tool for music creation and composing.

In the old days, Apple Macintosh computers were exclusively used for music and audio. In the last few years, the Microsoft Windows operating system has been adopted by musicians and recording engineers. Today, whatever you would like to do on a computer, you can do it equally on either machine. Traditionally, you will see more Macintoshes than PCs in recording studios, but that's changing. Talk to other musicians and try out both the Mac OS and Windows before making a big purchase.