MOTU’s MX4 virtual instrument works as a plug-in with Digital Performer, Pro Tools and Mac OS X Audio Units-compatible software. It combines subtractive, wavetable, FM, AM and analogue synthesis to provide a wide range of sounds. If you like vintage synths such as the Prophet 5 or PPG Wave, you’ll find plenty that you like.

Screen shot of MX4

Users can create waveform morphing effects, hard sync effects as on the Prophet 5, seemingly limitless filter effects, and complex modulation effects.

The main window is divided into ten sections. At the top is the Presets section for managing the patches, with the Status section to display parameters to the left and the Master section with its global controls to the right underneath. The Oscillators, LFOs and Mixer are underneath these, with sections for Filters, Envelopes and Modulation below again. At the bottom, the Effects section contains Chorus and Delay.

MX4’s 32-bit internal resolution gives it a tremendously wide dynamic range and you can work with 24-bit digital audio at sample rates up to 192kHz. One neat feature is the ability to work out the polyphony required to play the current piece of music. The maximum polyphony per MX4 is 256, but ideally you should set this to just the number required. The Status LED displays the number of voices required and you can set this number in the Master section.

The MX4 competes well with its rivals. You can recreate the sounds of classic synths such as the Moog Modular series, or you can create more contemporary sounds. It has three oscillators with modulatable waveform symmetry and hard sync, six variable waveshape LFOs and four ADSHR envelopes.

Choose Hold Me from the basic MX4 sound bank, hold down a note or chord, and you will hear a soulful rhythm playing on your note or chord – calling out like a ghostly Morse code message. Or try the Sub-Bass patch from the Basses section to hear just how low it can go. Try the Syn-Drum in the Drums section or the Arp 1 from the Arpeggiate section, which produces interesting delayed repeats. My only criticism is that the patches are the kind you use to put the icing on the cake rather than the solid staples you’d use to build most types of music.


MOTU should get some kind of award for the MX4. The user-interface is a joy to look at and to work with, and the banks of patches include sounds that compare very favourably with its competitors.

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