Is your dance floor half empty... or is it half full? Either way, that's no good: as a DJ you want it to be jam-packed, with elbow-manoeuvring room only. That's mostly a matter of picking the right tunes and judging the mood, but your skill on the decks helps, especially as a dance DJ.

With DJ Mixstation 4 it becomes a matter of skill on the virtual decks, as you can plug in a laptop and scratch away on your MP3 collection (all without damaging your precious records).

The program automatically scans your hard drive, locating all music files and cataloguing them in a track-list window. The interface is presented in a smart, metallic finish, with lots of dials to twiddle and two virtual decks at the top of the screen. However, the track-list and play-list windows let the side down somewhat, looking like rather naff, standard, Windows menus in comparison.

Playing a tune is as simple as dragging it from the track-list and dropping it onto one of the decks, then pressing play. It's possible to place markers at any point in the song, so you can immediately cue up to them, or you can loop a track from certain points. The main toys, however, involve scratching and the jog wheel.

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Scratching is achieved simply by clicking on the waveform display of the song, holding down the mouse button and pulling left or right. It's quite effective, even more so if you switch on vinyl mode and use the jog wheel to scratch.

When vinyl mode isn't engaged, the jog wheel lets you alter the pitch, tempo or key of a tune, with some interesting results. A further slider lets you modify the tune permanently so you can, for example, up the tempo 10 percent if you want to play a song a touch faster than normal to get the crowd's juices really flowing.

There's also an effects panel which can be used to add echo, flange, distortion and so forth, and naturally there are master controls for the volume, bass and treble of each deck. Of course, the most important control is the cross-fader, which fades from one deck to the other.

When you pull this across, it brings in the sound from the other deck gradually, and there's a handy BPM matching button. This matches the beats-per-minute of one song to another, so the transition is as seamless as possible. Mixstation 4 also offers an auto-fade function, which does exactly what it says on the tin (fades across for you). It does this in a reasonable, albeit slightly stilted manner.

If you have two sound cards installed, the program lets you specify one for use with the amp and speakers, and you can run the other through a set of headphones, letting you listen to the second deck independently through them.

Fortunately the program's easy to use all round, and the manual is decent enough, but it's disappointing that the in-program help takes you to a blank page on the eJay Web site (at the time of review). This means there's no way to check up on certain specifics, such as what the program's keyboard shortcuts are. Despite this, Mixstation 4 remains a well designed laptop DJ'ing package.

Mixstation 4 is an impressive DJ'ing program, which is generally easy to use even though the online help is mysteriously missing. The suite provides a wide range of effects, including a decent approximation of scratching, pitch bending and the like.