WHAT YOU NEED
> iTunes
> Algoriddm djay 1.2 free
> Potion Factory Tangerine 0.9.2 beta free, optional
> Audio Hijack Pro $32, optional

1. Drag-n-DJ

Launch djay 1.2. All of your iTunes tunes will be automatically listed in the native play list. Djay provides the standard features of any good DJ set up: a mixer for increasing the aural presence of one song over another in playback, dual equalizers, pitch, and tempo sliders for adjusting the sonic character of your songs, cue points for moving from points of one song to another, as well automation for when you’re ready to try crossfading (moving between two recorded songs). If you were thinking ahead, you’ve already listed your beats-per-minute (BPM) in your iTunes library. And if you didn’t know this already, being able to match the BPM rate will let you weave different songs with different tempos together while maintaining an entertaining consistency in your mix (translation: slowing down “YMCA” so that it segues into the slower and more down tempo “Feelings”). If you haven’t done this, djay 1.2 can do it for you automatically with a click on the Sync button along the bottom of the app window.

However, since we found djay 1.2’s native BPM feature to be a little slower than desired (a definite caution for live mixing), and many of us get paranoid about having all of our DJ eggs in one app basket anyway, there’s some cool freeware that you can use instead. Potion Factory’s Tangerine 0.9.2 beta on a 1.83GHz Core Duo iMac can BPM-analyze three songs a second in your iTunes library, which sets you up quite nicely to start beat-matching and even scratching, if it suits you. (Scratching, de rigeur in lots of hip-hop based DJ sets, used to be done by dragging the turntable needle across the vinyl. But that can all be done right here.) You want to avoid sudden volume peaks and strive for a barely noticeable sense of one song moving to the next. In iTunes, there’s also a Sound Check feature that does exactly the same thing, optimizing track volume for smoothness (the Join Tracks feature does sort of the same thing when you’re importing music).

2. Get This Party Started Right

Before you start waving people over, there are a few things you must do after choosing the songs you’re going to mix.

First, set your equalizers (EQ): These are filters that let you boost certain frequencies. In general, party people are partial to bass signals, so it’s OK to boost these. Keep in mind, however, that most modern music is already so well mixed that a light touch should be used when setting your EQ. You’d probably be fine zeroing out your EQ too.

Next, set your volume using the sliders between the two virtual turntables. We suspect that the output on these is +15 dB, but don’t try to have any sort of mix be this loud even if the newbie temptation is just to keep cranking it. Yes, up to 11 (for you Spinal Tap fans) might seem cool, but it will bleach the color from your mix if all you do is play it loud.

The last step is to set your tempo and pitch. Changing the tempo of the music is essentially stretching or sinking the time the music plays, which also changes the pitch. Shrinking the time the music plays in causes the pitch to rise (think The Chipmunks), while stretching it makes it go lower (think Darth Vader). What you want to do with your party affects what you do here. Our advice though is to leave them be. It might be “art” that you’re making, but it may not make people want to dance.

3. Get Jiggy with It: Mixing 101

So now you’ve got your event-appropriate songs ready. If you want the easy way out at this point do a slow fade on song 1 while slowly bringing up the volume from zero of song 2. This is effective but not nearly as impressive as using the mixing feature to move from song 1 to song 2 which, if your volume levels are consistent, should not sound so bad at all.

In our case, we chose “Hands Up” by the AC/DC-esque band Big Business along with rap star 50 Cent’s paean to armed robbery, “Ski Mask Way,” to mix into what we like to call art, and you’d probably call annoyance. To effectively match beats, though, they have to be playing at the same tempo, and the tempo in most songs changes from moment to moment. Toggling up and down to make minute tempo adjustments to the songs’ relative tone and adjusting EQ to taste, you then have to use the cues to mark entry points in the songs that when mixed or played simultaneously have the bass and drum presence falling relatively in synch with each other. This can be quite difficult and while we don’t suggest you try this while DJing a party, it’s tons of fun at home.

4. Cut It On Wax

Some DJs’ theory of DJing tends toward the psycho-mystical and a belief that the enjoyment of the party moment should never be preserved—because how can you really catch a butterfly? (Right, we have no idea what that means either.) If, like us, you’re ego-driven enough to want to record your DJ outings, see “Free Your iTunes Music from FairPlay." Audio Hijack Pro is perfect for recording the music you’ll be playing for the party on your Mac. Use it. Live it. Love it.