A little of this, a sample of that

Mashups are tracks that combine samples of one familiar song with the recorded vocals from another, such as “Switchin’ Alive,” with Will Smith rapping “Switch” over the Bee Gees’ “Staying Alive.”

The idea is to combine two musicians who have nothing to do with one another stylistically, in order to create something danceable and new: Vanilla Ice rapping “Ice Ice Baby” over Wang Chung’s “Everybody Have Fun Tonight.”

And with a computer and a couple of pieces of free software, you can join the decades-old – yes, decades – mashup craze.

Jazzmen took apart entire songs and put them back together in ways that are fresh but slightly familiar because you’ll hear the original melody.

And hip-hop crews in New York City parks would use one turntable to repeatedly play a chunk of a familiar song while a second turntable spun and an emcee added spoken rhymes. While not exactly a mashup, the effect was recasting the familiar in an unfamiliar light.

With today’s computer technology, digitized songs can be mashed together and made to sound like they were recorded that way.

To hear what we’re talking about, visit www.PartyBen.com, home of KITS-FM DJ Party Ben, who creates mashups for his radio station, Live 105 in San Francisco.

Creating your own on a computer running Windows XP is relatively easy. Go to AcidPlanet.com and download the free software Acid Xpress. It’s a program that can slow down a faster song and speed up a slower song so that the two songs have the same tempo and you can play mix and match.

AcidPlanet.com even runs contests in which artists such as Gorillaz, Trent Reznor and Madonna give you access to snippets of their music that you can remix using Acid Xpress. The remixes are uploaded, judged every month or so by the AcidPlanet staff, and the winner gets free stuff.

(Other programs do the same kind of magic, particularly Ableton “Live,” at www.ableton.com. The free demo version, however, won’t let you save your remixes the way Acid Xpress does.)

You don’t have to rely on Acid Planet and other sources of free samples, though.

Using the free program Audacity, at audacity.soundforge.net, you can slice up bits of your favorite mp3s and throw them into Acid Xpress to create loops that play over and over and form the base of your song.

Finding vocals to go on top is a different matter.

If you live near a record store, check for LPs that contain a cappella versions (or, vocals-only) of popular songs.

These are readily available for hip-hop and some dance tunes, as the labels making these records want to make it as easy as possible for deejays to remix their songs.

(Remixes lead to more plays on the dance floor, which could lead to more popularity and more sales.)

With Audacity and an RCA-to-stereo-miniplug adapter from any electronics store, you can record the output of your turntable (from the Line Out jacks) into your computer (using the headphone jack).

Once you’ve made a tune you like, play it for friends and family, but don’t try to make money off it.

Creating mashups for personal use is fine, but if you try to sell them, the affected record companies will send their lawyers to bang on your door.

Lawyers aside, mashups are fun to make and dance to. Check ‘em out.