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Alesis Air Synth

Motion-controlled Synthesizer
Published March 2003
By Paul White

Alesis brought us Air FX, a motion-controlled effects unit, just before they ran into financial trouble in 2001, so the planned synth version never really appeared at the time. Now they're back, the Air Synth is with us at last...

Alesis Air SynthThe Alesis Air Synth is the second product in the 'Air' series, the first being Air FX reviewed back in SOS January 2001. The unique feature of these products is that all control is via an infra-red sensing array beneath a perspex dome that detects hand movements in three dimensions, making it possible for several parameters to be controlled with a single gesture. IR light is emitted from the centre of the dome, and is received by four sensors positioned around the outside of the transmitter.

Like the Air FX, the Air Synth operates on a set of presets, where no user intervention is possible other than to adjust the global tempo for the benefit of those patches that include a tempo-related or 'sequence-based' element (more on these in a moment). The closest analogy I can make in describing the Air Synth is an optical theremin, but even that analogy can only be taken so far, as the Air Synth doesn't have the same pitch range as a true theremin. On the other hand, it can produce a whole range of sounds and effects, not merely a 'singing waveform'.

Describing the controls and facilities is easy. Air Synth has phono outputs (stereo) that are wired in such a way that they can be mixed to mono using a 'Y' cable. I assume from this that there are resistors in series with the output, as that's the only way to achieve this safely. There are also phono inputs, which in this case allow an external stereo audio source to be mixed with the output from the Air Synth in situations where no mixer is available. The nominal operating level is -10dBV.

Alesis Air SynthPower comes from the included external mains adaptor and a rotary dial with integral switch is used to select and load presets as well as to 'freeze' sounds and sequences that develop as they play, and to mute the metronome for patches where one is used. In all, there are 50 presets, with an extra position between preset 49 and preset 00 that allows you to reset the global tempo by beating time over the optical sensor dome.

The first patch (00) sounds to me like a perfect morph between a helicopter and a pneumatic road drill, and when you wave your hand around over the sensor, the sound pans and changes timbre as though it were moving into the distance — so if you ever need to dub helicopters onto a very low-budget film, this is a quick and easy way to do it. Most of the other sounds can be broken down into pads, sound effects and synth sounds, though there are also percussion sound sets, including one where you can layer a sequence of kick, snare and hi-hat sounds, then 'freeze' the result. Of course, all these 'sequence'-type effects are lost once the power is switched off, but as a basis for creating samples and loops, they are extremely easy to use, with plenty of scope for serendipitous discoveries.

Alesis Air Synth £160
  • Learning curve not at all steep!£160
  • Can create an interesting range of musical and rhythmic effects and sounds.
  • The sounds can be controlled very intuitively via the IR interface
  • Everything is based on presets, with no facility to edit or tweak.
  • No MIDI Out for controlling other sound sources or for storing controller 'moves' into a sequencer.
While it can't really be considered as a serious musical instrument in the traditional sense, the Air Synth makes a wide range of interesting sounds and noises that respond beautifully to the user's hand gestures. And it's fun!


The other 'sequence-based' presets work similarly, but use musical sounds rather than percussion noises, some generated randomly as you wave your hand around, others playable — up to a point. As soon as you hear something you like, you can press the data wheel to 'freeze' the loop so that it keeps playing without accepting any further changes. Most of the rhythmic sequence-based effects have a metronome tick which you can mute by pressing the data wheel, and from what I can tell, the results are quantised so that they sound musically meaningful, no matter how sloppily you play.

Of the more esoteric musical sounds, there are electronic digeridoo effects, R2D2-like chirps, random electronic vowel sounds, FM bell-type modulations, feedback/distortion sounds and patch 36, which is described in the manual as one of the most annoying sounds ever made. To me it sounds like a robot that's had one too many pints of Castrol the night before and is busy throwing up into something metallic while reading the news aloud and using an electric razor to shave at the same time! On top of that, there are ring-modulated sounds that shift as you wave at them (very Doctor Who), electronic percussion ensembles, theremin-type sounds with vowel-formant filters and complex synth pads, some freely pitchable and some quantised into semitone steps. If you'd had one of these in the '50s, you could have made a fortune doing the effects for sci-fi 'B' movies!

Using the Air Synth

Playing the Air Synth is pretty easy once you twig that the percussive presets require more positive gesticulations than the synth and sound effects patches, presumably to stop false triggering. If you imagine you're hitting a drumskin just above the dome, the percussion sounds respond well. It's important to experiment with the X and Y axes as well as distance, because most patches make use of all three dimensions, though a few use only two. Exactly what happens when you move your hand depends on the patch. It may change the pitch and/or timbre, you may trigger new sounds, or you may alter the modulation applied to a sound.

With the random rhythmic sequences, there is a short delay after placing your hand over the dome before the sound starts, so the trick is to keep your hand there until you hear a good bit, then press the data wheel with your other hand to capture it. Those patches that generate different quantised pitches or percussion sounds do so dependent on the angle at which your hand approaches the dome, so with a little practice, you can play something vaguely tune-like, though don't expect to achieve anything too ambitious.


Alesis Air SynthPhoto: Mark EwingAir Synth is easy to use and a lot of fun, but its ability to play musically meaningful phrases is limited by its simple interface. Even so, you can get some great sounds and effects out of it, not to mention generating very sampleable percussive and melodic rhythm sequences. I particularly like the manic vowel sounds and formant-filter effects, which DJs and dance producers could use to spice up their mixes or live performances. The more 'silly' sound effects can also be fun; they include (in addition to what I've already mentioned) simulated fireworks, engine sounds, starship 'bridge' noises, detuned radio noises, and electronic wind noise.

There's no MIDI Out, as is also the case for the Air FX, which I've been told is because the sound is reprocessed every sample, something that the MIDI protocol could never even think of keeping up with. Even so, a thinned-down MIDI data stream working at normal MIDI sub-light speeds would still have been useful in many applications, so this remains a bit of a missed opportunity — both Air Synth and Air FX would have made great MIDI controllers.

While you may never become a musical virtuoso on the Air Synth, it sounds interesting enough to be useful in many types of modern music production, as well as for producing sound effects, or for adding audio and visual interest to a live performance. For me, its best feature is its immediacy. Just plug it in, flutter your fingers over the IR dome and you've got a result. It offers instant gratification at an impulse-purchase price!

infop.gif £159.99 including VAT.
infot.gif Numark-Alesis UK +44 (0)1252 341400.
Published March 2003