The mash-up. You take the music from one song and overlay the vocals from another song to create something new, sometimes with surprising results. The fun comes not only with how well the source materials unexpectedly fit together in terms of melody and chords, but also with the juxtaposition of genres.

This is different from writing your own song over a recognizable piece of music (e.g. Sugarhill Gang rapping over someone playing the bassline from “Good Times”) — you need two pre-existing songs for a mash-up. Sampling also exists on a separate plane, taking a small part of a song and singing over it. The technology of the 20th century only allowed you to take snippets, but that would soon change.

As the 21st century dawned, increasingly sophisticated (but surprisingly user-friendly) audio software became available to normal human beings on their home computers. You no longer needed a million dollar studio setup to make music like the pros. One of the techniques this software allowed you to employ was called OOPSing. OOPS stands for Out Of Phase Stereo and it provided the ability (although not always perfectly) to isolate vocals by partially or entirely canceling out the musical backing or, vice versa, removing the vocals.

At the same time, the advent of CDs and their huge storage capacity meant record companies and artists felt the need to fill up every second of available space, which led to albums and singles adding a wealth of bonus tracks in the 90’s. This also meant bands needed more material and would sometimes release instrumental backing tracks or a capella versions of songs. All of these would prove useful.

In 2001, DJ Roy Kerr, plying his trade under the name The Freelance Hellraiser, released “A Stroke Of Genius,” which took the music from “Hard To Explain” by The Strokes and added the vocals from Christina Aguilera’s “Genie In A Bottle” (what techniques he used for this are unknown). Although a few proto-mashes had appeared in the clubs before this, “A Stroke Of Genius” seemed revolutionary at the time when presented to a mass audience. The song was actually an unofficial bootleg, released both as a white label single and as an mp3 audio file into the wilds of the internet, and it immediately went viral in the music-sharing communities, helping to kickstart a wave of mash-ups over the next decade and bringing the term mash-up into the musical lexicon.

The idea for a mash-up of two full-length, pre-existing songs goes back to at least the early 80’s, however. In 1983, Italian producers Club House somehow got the notion that Steely Dan’s “Do It Again” would fit well with the music from Michael Jackson’s “Billie Jean.” So they mashed them up. The difference in this case is one of technology since there was no way to procure isolated vocals at the time. It’s difficult to discern if the music is the original (parts seem to be, and other parts not so much), but the vocals are definitely not Donald Fagen. This, however, is what artists have been doing on YouTube for the last 10 or 15 years — rather than use the original source material (messy in terms of copyright) like DJs in the 2000’s, they now perform the whole thing themselves as a kind of double cover. Here’s where that started: