MOTU MX4 2.0 (Mac)

Virtual analog synthesis can take either of two main paths: one emulates classic instruments, and the other blends physically modeled analog-synthesis

Virtual analog synthesis can take either of two main paths: one emulates classic instruments, and the other blends physically modeled analog-synthesis components, digital waveform generation, and the signal flow and enhanced control afforded by modern computers. MOTU MX4 is a relatively recent addition that forges classic and unique new sounds from a variety of modulation options and a cross-fertilization of vintage digital and analog synthesizer technology.

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FIG. 1: Along with all the other parameters, MX4''s Main page supports a beautiful LFO window that resembles a camera lens. The lens graphically illustrates changes you make to the LFO parameters using the surrounding slider knobs.

Installing MX4 couldn't be easier; the provided iLok USB key authorizes it, and you're ready to go in just minutes. MX4 works only under Mac OS X with MAS, RTAS, and Audio Units hosts; it's unfortunate that there's no version for Windows. I ran MX4 on my dual 1.42 GHz Power Mac with OS X 10.3.9 and 2 GB of RAM. Hosts included Ableton Live 5.0, Apple GarageBand 2.0.2, Granted Software Rax 1.2.3, and MOTU Digital Performer 4.6.

The Cook's Tour

The basic complement of synthesis tools includes three oscillators, six LFOs, and four envelope generators (see Fig. 1). At first glance, the synth presents a relatively conventional subtractive synthesizer signal flow from oscillator to mixer, filter, and amp, but there's plenty more. One of MX4's great beauties is the extraordinary depth of programming capability that is neatly tucked just out of sight (see Fig. 2). For example, rather than clutter the screen with nests of virtual patch cords, MX4 takes full advantage of contextual menus invoked with a mouse-click and with the Control and Option keys, which can, for example, link an LFO to an oscillator or define a modulation range. Likewise, other modifier keys combined with mouse-clicks can pull up modulation-routing menus, reset modulation starting points, or create fractional parameter values.

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FIG. 2: Although MX4''s signal flow is familiar and relatively simple, quite a few additional controls are hidden with key commands, minimizing onscreen clutter.

At the top of each MX4 page is a small horizontal strip that holds basic page- and file-navigation options. Starting from the left are menus for bank and patch selection; you can scroll incrementally with plus and minus buttons or pull down the menus for a better overview of choices. Next, the Save button lets you immediately write your patch tweaks to the current location. Extra kudos for the A/B button — I'm used to an edit/compare feature on my hardware synths, and very few virtual instruments have that capability. Revert removes changes from RAM and returns the synth to its original state.

The next group of buttons in the strip accesses MX4's four pages: Main, Mods, File, and Random. Most of the programming happens on the Main page; the Mods page (added as of version 2) focuses on various rhythm- and tempo-based programming refinements and on additional modulation-shaping tools.

Each oscillator draws from an extremely generous selection of waveforms. Choices range from traditional sine, sawtooth, and rectangular waves to white and pink noise and a batch of unique and interesting wavetables. Version 2 adds band-limited, antialiased versions of all the prior version's waveforms. You select them incrementally with plus and minus buttons or click on the waveform name and use the pull-down menu.

You can wring lots more tonal variety from the synth's FM capabilities. Oscillator 3 modulates 1 and 2, and you control the amount of modulation to each carrier. In conjunction with the rich assortment of wavetables, the timbral variations are practically limitless.

Modulation in All Things

A slider that controls waveform symmetry invokes typical pulse-width modulation effects when you apply it to a rectangle wave. Modulating the symmetry of a sine wave can bring it close to a sawtooth wave's harmonic content. If you select a wavetable rather than a traditional waveform, though, you can use the oscillator's Index slider to adjust its harmonic content based on the slider's position in the wavetable's cycle, or you can sweep it for continuously evolving sounds. Modulating wavetable symmetry is rather unpredictable because the harmonic content depends on the portion of the wavetable's index you're modulating (see Web Clip 1).

Using a slider to modulate symmetry is only the tip of the sound-design iceberg. You can also modulate symmetry and the wavetable index with any MIDI Control Change (CC) message to produce powerful sounds with a pulsating inner life (see Web Clip 2). What's more, thanks to the Shaper section, you can have modulators modulating other modulators in as complex a daisy chain as your CPU can handle.

The LFO window is a gorgeous piece of design, resembling a frontal view of a camera lens. Sliders surrounding the lens set LFO Rate, fade-in time, delay, starting phase, and waveform symmetry. Changes to those parameters are reflected graphically inside the lens. Tabs at the lens's upper-right quadrant let you select from each of the six LFOs.

MX4's two multimode filters sound glossy and smooth, but they give you plenty of latitude for grit and distortion. Each filter offers highpass and lowpass varieties as well as bandpass and band-reject types, with 6, 12, 18, and 24 dB slopes. You choose a filter configuration in the Topology window, which has a pictographic pop-up menu that illustrates the signal flow of the two filters and the distortion section. If distortion isn't enough, applying FM to the filters adds a bright edge and an animated buzz to the timbre.

Four razor-sharp, responsive envelope generators can modulate any continuous parameter. Although Envelope 1 is hardwired to amplitude, all envelopes can modulate multiple parameters. MX4 adds a delay stage before the attack, and a hold rate between sustain and release. The additional stages furnish more graceful tailoring of attack and release stages than a typical ADSR.

MX4 is a veritable modulation theme park. The key to its extensive modulation capabilities is the Source and Shapers panel at the lower right of the Main page. The combinations you specify there can provide endless permutations within a complex modulation signal flow. A radio button to the left of the Source column lets you select a modulation source. You can shape the mod source by making a selection in the Shaper column. If you Option-click in the center notch of a modulated parameter's slider, the slider will split in two, letting you define high and low modulation ranges. The Information window displays the selected parameter, the base value (the value that the modulation starts from), and the modulation range. The window also displays the number of voices in use.

Oscillatin' Rhythm

The majority of the Mods page furnishes rhythm-based modulation components such as a programmable gate, two types of onboard sequencers, and an arpeggiator. As with the filter section, the Mods page offers variable topology for the Pattern Gate and two effects slots; you can feed one element into another in any order you choose by dragging the three modules (see Fig. 3). Mods are not constrained to simple triggering of notes or amplitude; shapers can affect timbral changes or modify other modulators.

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FIG. 3: The Mods page hosts a variety of rhythm-oriented modulation devices and shapers. The lens in the center displays scaling and inversion shapers

Invert and Transform shapers provide a terrific graphic display for scaling modulation; inverting filter envelopes is great for those chirping, resonant synth basses. The Quantizer is a bit more esoteric, but you can shape modulation by pitch; clicking on notes in the keyboard graphics lets you lock modulation values to selected pitches. (Here's your opportunity to shape an LFO in G Mixolydian.) MX4 can process external audio in several ways: you can blend it with the instrument's oscillators, apply filters and effects, or process it with a ring modulator; and — in the Mods section — you can input sound so that its amplitude serves as a control source or shaper with the envelope follower.

Pattern Gate slices MX4's audio output into rhythmic pulses. You can alter rhythms with its step-sequencer-style interface and change the pulse envelopes. A similarly arrayed Trigger Sequencer can force any of MX4's envelope generators into discrete rhythmic steps. Each patch can hold its own programmable arpeggiator and pattern sequencer. All rhythmic modulators sync to the host tempo and let you set a rhythmic value and swing amount.

Animation Festival

Although MX4 can emulate a variety of vintage synthesizers, comparisons to any particular classic instrument are irrelevant. The plug-in can dish out sounds ranging from raucous, in-your-face leads and chunky brass ensembles to thick or gauzy pads — all animated with tons of timbral and harmonic motion.

Among my favorite factory patches are Held=Pad, Fast=Pluck, which sounds like the result of some unholy congress between a didgeridoo, a dentist's drill, a vacuum cleaner, and a vocoder-processed drum machine. A patch called MS Windows 2058 for Washing Machines superimposes astonishingly eerie, bagpipes-from-hell melodies over a pulsing drone (see Web Clip 3). Other standouts include the distant, distorted cloudiness of We're Through and the drunken, single-finger melodies of Happy Hour for Chips.

MX4 is somewhat processor intensive, but it provides facilities to reduce the toll on your CPU, such as toggling the effects on and off and limiting the number of voices per patch. If you don't need a heavy-duty multiple-filter configuration, simpler filter arrays and coarser slopes can help ease the drain.

Documentation is more than thorough. My copy arrived with a lucid manual and a separate booklet covering the multitude of features in version 2. The manuals are rife with terrific programming tips. A section in the update pamphlet gives an overview of five important concepts for programming MX4. Many of the tutorials reference a bank of example patches.

Love Notes

I am thoroughly enamored of MX4. You can delve deeply into its first-rate modulation capabilities, harness its intelligently arranged Randomization page, or simply tweak a few parameters and create something new and interesting. A few items for future development are on my wish list, however. As a MIDI guitarist, I wish that it had some multitimbral capabilities, or at least the ability to allocate a limited number of voices in a single instantiation over multiple MIDI channels. If your CPU can handle it, though, you can run multiple instantiations assigned to different MIDI channels. Hopefully, MX4 will become a standalone instrument, too.

This review barely scratches the surface of what is available in MX4. MOTU's Web site holds a generous number of MX4 audio demos. Better yet, you can download a 30-day, fully functional copy of the synth. Don't forget to come up for air and food.

Former EM assistant editor Marty Cutler fights bad software manuals in New Jersey so you don't have to fight them at home.


MX4 2.0

soft synth plug-in

PROS: Capable of lots of timbral motion. Elegant and extremely flexible modulation scheme. Excellent time- and tempo-based controls. Can use audio input as oscillator and control source. Terrific documentation and tutorials.

CONS: No Windows version. No standalone version.