A MIDI (Musical Instrument Digital Interface) song file contains an exact recording of every single note played by the composer of that piece of music precisely as they played it on their music keyboard.
MIDI first appeared in 1983 as cutting edge technology developed in collaboration between electronic keyboard giants of the day including Roland, Korg and Yamaha. Professional musicians used the MIDI protocol to synchronise other compatible electronic devices from their keyboard allowing them to play multiple instruments remotely and to create many new and unusual sounds which became the trademark synthesiser soundtrack of that decade.
Unlike CDs or MP3 files, MIDI files are specifically designed to be edited and are intended to be used for performance or as a learning tool, rather than to be played back purely for listening purposes. For example, if you were learning or practicing a song, a MIDI file would allow you to change the key, adjust the tempo and even remove or damp down selected instruments as you wish. Their versatility makes them ideal for karaoke or as background music for home videos, websites etc; or simply to have fun with.
In order to play back a MIDI file, you require a sound card able to generate everyday instrument sounds such as piano, drums etc. Most modern computer systems will already have this technology in place. MIDI files are usually very small and thus can be easily edited on any PC. Their exceptional versatility makes them ideal for use as backing tracks over which you can lay down your own vocals or instrumentals.
There are thousands of free to download MIDI music files available via numerous internet websites, FindMIDIs.com being one of the biggest and a good place to start. There are lots of sound editors and media players which will enable you to open your MIDI files and most computers will have this software already in place. Once you have downloaded the files, you can transfer the songs to whichever instrument you with to use them with and let the fun begin!