Step up to the orange rectangular device and wave your hand over it. A whooshy, almost alien sound wafts through the air. Is it a sci-fi movie? A virtual-reality video game? No, it's the Alesis airSynth ($249).

Falling somewhere between pro instrument and toy, this pint-size module offers a cool — but limited — selection of synthesizer sounds, all controllable using hand motions like those of a theremin player.

The airSynth can sit on a tabletop or be mounted on a mic stand. It's being marketed to the remix crowd, so it features a pair of RCA outputs rather than ¼-inch jacks. Plug the airSynth in to your amp or sound system (you need adapters — optimally, a Y-cable — if you're going into a ¼ inch input) and you're ready to dial up one of the 50 patches: turn the Program knob to the desired preset and press. Then, wave your hand over the domelike control surface to play the selected sound.

HAND CONTROL

The airSynth uses subtractive synthesis to produce fat, resonant tones. These are controlled by the Alesis AXYZ interface, an infrared sensor that offers three dimensions of control. The x-axis is controlled by moving oyur hand left to right, the y-axis by moving front to back, and the z-axis by moving up and down.

Each axis is assigned to a different parameter, and the parameters vary from patch to patch. For instance, on Pet Sounds, the x-axis controls pitch, the y-axis controls brightness, and the z-axis controls volume. Some patches can be controlled by tapping on the dome, which is useful for playing percussive sounds.

AIR SOUNDS

The patches are divided into four basic groups: Tone, Percussion, SFX, and Rhythm. The Tone category offers pitched sounds, although the controller isn't ideally suited for precise melodic control. With a little practice, I was able to play simple melodies (with some expressive vibrato), but pitch accuracy was difficult to maintain. Many of the sounds in this category are cool: my favorite is the analog-sounding Demon Pad that has a feedback component controlled by the y-axis.

The Percussion patches — bells, claps, and other percussive timbres — sound okay but are difficult to precisely control, even when tapping the dome. The SFX sounds are much better overall. These include a great tuning-between-stations sound, gunshots, bubbles, and sci-fi effects. When you select a Rhythm patch, the airSynth turns into a basic sequencer for creating drumbeats, random bass patterns, and the like. Unfortunately, there's no way to save any of the patterns you create.

However, you can take advantage of the airSynth's hold feature by tapping the Program knob as you play. Depending on the patch, this will lock in a groove or sustain a note.

WHO ARE YOU?

So who will want an airSynth? It's definitely aimed at the DJ market, especially at the entry level. But the airSynth will also appeal to bands that don't have a keyboard player but want to add synth effects to their arrangements. What's more, the hand motions required to play the airSynth will add visual appeal.

Although limited by its finite sound set, the airSynth is still a pretty cool device for the money. I hope that future incarnations will offer a wider selection of tones, user programmability, and MIDI capability. Those additions could make the airSynth a formidable instrument.

▪ Rating (out of 5): 3

Alesis Distribution LLC; tel. (310) 301-9563; e-mail info@alesis.com; Web www.alesis.com