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How MPE Unlocks New Dimensions of Sound

Revealing new frontiers of creative manoeuvrability, MIDI Polyphonic Expression (or MPE, as it’s better known) allows for more intricate and natural sculpting of electronically-generated sound.

What is MPE?

Depending on how plugged-in you are with the latest innovations in music technology, the term MIDI Polyphonic Expression (MPE) will elicit a different response. Those that aren’t cognizant of how this new standard works, will likely have some uncertain familiarity with the term, thanks, perhaps, to the innovations of Roger Linn and ROLI. Others, meanwhile, likely those just taking their first steps into synthesis, may be wholly befuddled by yet another new acronym.

Explaining what MIDI Polyphonic Expression does to the uninitiated requires us to first explain just why it’s proven to be a necessary invention. Time was, performing with an electronic instrument, such as a polyphonic synthesiser was a fairly linear affair. Hitting a note on the keyboard would trigger its sound and, while expression controls such as the pitch-bend and the modulation wheels implemented wide-scale changes to the overall output sound, via continuous controller (CC) messages, nuanced adjustment of the individual notes within a chord was an impossibility. This led to many coming to regard the synthesiser as more of a stiff, ‘programmable’ instrument, as opposed to something you could fully express yourself with.

Developed initially as Multidimensional Polyphonic Expression, prior to being formally standardised by the MMA as ‘MIDI’ Polyphonic Expression, MPE offers per-note articulation light years removed from the simple CC parameters of non-MPE keyboards.

MPE uses 16 MIDI channels, this means that detailed control messages are both sent and received at the same instantaneous speed as note-press information, the specific data instructions which detail how the note should sound emanate from precise specifics of how the note was pressed as opposed to the all-encompassing, positioning of wheels. Where your finger is positioned – and how it moves – communicates this information, meaning that more instinctive sonic design can be achieved.

This results, therefore, is a much more unlocked instrument that can provide the same levels of tonal flexibility and manipulation that you’d find when, say, bending a guitar string. Coupled with this is greater velocity feedback, almost akin to the breath-based scalability of a brass instrument (NB: MPE works fantastically on brass sample-performance)

A less daunting way of looking at MPE is by recognising that the format is ostensibly re-configuring the approach to *existing* X and Y-axis CC parameters, such as those typically attributed to the mod wheel for forward/back motions up and down a key (Y) as well as left and right (X), but with the added benefit of polyphonic aftertouch, velocity and gradations of finger-movement.

Resultantly, your performances can be hugely enhanced by working in the MPE domain. With gesture and pressure-based control, you can not only carve things like note resonance by angled control of your finger on the key or pad, but you can affect other parameters (say, the volume) simultaneously, while more naturally gliding between notes, and wringing out dramatically more exciting variations of notes and chordal shapes.

Peak Polyphonic Performing

Regarded by some as the biggest change in electronic sound since the invention of the synthesiser, MPE has had a slow and steady evolution, but now has become a widely accessible format for modern creative musicians.

One of the very first bona fide MPE-based instruments, came courtesy of production luminary Roger Linn (he of the revolutionary LinnDrum). The LinnStrument’s exploration of the MPE concept sprang out of Roger’s desire to ‘save the note’, particularly in a landscape increasingly reliant on sampling. Something Linn considered to be leading toward a somewhat flat bedrock on which to compose.

It was immediately apparent that the LinnStrument was not a traditional keyboard, with its banks of 200 blinking pads responding to five inputs – strike velocity, fingertip axis positioning (left/right and up/down), pressure adjustments and release. This astounding innovation was a step too far into the unknown for some, who hastily filed it away in the ‘experimental’ category.

ROLI brought clearer focus on what this new protocol could offer, with the company’s silicone-keyed Seaboard instrument becoming something of a flagship for MPE presentation. Though more traditionally laid-out than the LinnStrument (to the untrained eye, at least), its appealingly squidgy keys underscored how MPE served up a different approach to that of a conventional keyboard. It presented something of an epiphany to many who’d not been able to comprehend the appeal of MPE before. The Seaboard proved a success, and brought scores of new musicians aboard the MPE train.

After years of in-house development and collaborative synergy, the MMA formerly ratified the MPE standard – and changed that first acronym to ‘MIDI’. The president of the MMA, Tom White said “The efforts of the members (companies) of MMA has resulted in a specification for Polyphonic Expression that provides for interoperability among products from different manufacturers, and benefits the entire music industry.” From that point on, MPE’s acceptance has resulted in widespread support from all major DAWs, and a swelling range of hardware and software products that invite multidimensional control.

Among the leading lights in the world of MPE control are the following:

Roger Linn Design LinnStrument

The original MPE pioneer, the LinnStrument comes in both a 200 or 128 note version. It features a wide variety of play modes including strum mode, drum mode, polyphonic sequencing and arpeggiator. It’s aesthetically rather beautiful, too.

Keith McMillen Instruments K-Board Pro 4

This 48 key MPE controller may resemble a small keyboard to the untrained eye, but the Smart Fabric Sensors under each silicone key allow for full-range MPE control. It’s USB powered and class compliant, meaning it’s ready to work with minimal fuss.

ROLI Seaboard

ROLI are at the forefront of MPE instrument design, with the classy, silicone-keyed Seaboard being a byword for MPE control. ROLI have produced numerous variants, from the 49 or 25 key RISE to the more mobile ‘Block’ type . They’ve also brought to life some innovative new MPE instrument visions, such as the astounding Lightpad Block.

Haken Continuum Fingerboard

A different approach to MPE is underscored by Illinois based Haken Audio. The unique, smooth-surfaced Continuum has been around since 1999, and has adapted to incorporate MPE. Its keyboard-sensor (which dispenses with traditional keys) is now able to more effectively incorporate MPE, dubbed ‘MPE+’, to work more fluidly with the Continuum’s more precise attack trajectory.

Sensel Morph

The futuristic Morph is a tablet-sized pressure sensor which offers swappable interface overlays that vary for different applications such as beat-making, composition and performing. An ultra-modern way of interfacing with your music, there’s little else like it on the market.

Artiphon Instrument 1

A singular controller that allows for a guitar-like strumming and sliding approach to sound control, the MPE-ready Instrument 1 prides itself on re-orienting your conventional approach to MIDI with the precision and feel of a real instrument.

Modal Gets Multidimensional

Always keen to adapt to the latest technological developments, Modal provides MPE support to the vast majority of its synthesisers. It all started with the debut 00 Series. 2017’s operating system update opened the door to the integration and control of the line’s rich synth universe via MPE. Subsequently released models, including the ARGON, COBALT and even the diminutive SKULPTsynth also offer MPE parameter control as standard.

Using MPE instruments with Modal’s synth range typically requires you to wire in your respective instrument to the synth in question via the USB-MIDI Host Port at the synth’s rear. Next you’ll need to activate ‘MPE Mode’ on your synth’s display (found under MIDI Settings) or via the Modal app. Once your devices are switched on, you’re pretty much ready to go. You might find that your MPE control surface has its own interfacing software (such as the K-Board Pro 4’s dedicated app). It’s best to match precisely the settings between the controller and your Modal synth (e.g. the master channel, master channel count and pitch bend range) just so you don’t get any conflicts.

Many MPE control apps offer numerous ways in which to configure your MPE instrument, so make sure you familiarise yourself with how your controller’s bespoke software works, and how you can use it to configure your surface to set parameter thresholds for things like timbre, pitch, volume, vibrato, effect levels and a whole lot more. Take the time to learn how to most effectively control your sound, and think about bringing out aspects such as filter cutoff and pulse width as now performable facets.

Sonic Sculpting

While it’s often tempting to go off road straight away and explore the astounding depths of the multidimensional rabbit hole, we’d recommend you take your first steps into this new world by trying something you’d previously only performed pre-MPE. From that starting point you can start to add more performance character to your arrangement. How about a bit of high-octave pitch bending while your left hand keeps things grounded with stable chords? Or, try the natural dynamics of how your fingers hit each note, while the fingers of your other hand do the complete opposite (if you can physically do it, that is!) These easing-in approaches allow you to hear how MPE smoothes out the rigid norms we’d previously been constrained by. When you’re initially performing with MPE, it’s best-advised that you learn how to edit and sculpt your performances into your mix (like any performance instrument, really). Always remember, the track is king.

While Modal’s original 002 and 008 keyboards and 002R and 008R rack units gained MPE in the aforementioned retrospective update, many of the company’s later synths, as well as the diminutive SKULPT synth, were conceived with this new performing standard in mind. SKULPT (particularly the SKULPTsynth SE) is the most affordable way into MPE-based polyphonic experimentation – particularly if you pair it with an affordable MPE instrument such as ROLI’s Lightpad Blocks or the Sensel Morph. Sporting two wave groups per voice, four oscillators and state-variable 2-pole filters which morph through low to high-pass filters with ease, interfacing with an MPE surface unshackles the SKULPT as a living, breathing and hugely powerful instrument, despite its size.

Released in 2019, the ARGON8 wavetable synth took Modal’s years of learning and housed it within an aesthetic blend of past and future. Sporting true 8 note polyphony, 64 oscillators with 4 per voice in all modes, 120 wavetables and 28 wave-shaping processors, not to mention three dedicated envelope generators, alongside two-pole resonant filters, the ARGON8 was a beacon of exemplary synth-design. While mooted from the start, MPE support was finally injected into this jam-packed workstation via software update v2.0. This was also applied to the 61-key 8x and its desktop module the 8M.

Hot on ARGON’s heels came the COBALT range, and with it, an eight-voice, extended virtual analogue synth for the ages. MPE support was a launch feature of this advanced synth, presenting the universe-sized expressive capabilities of this new standard from the outset. COBALT makes MPE support a whole lot easier, with Y-axis slidability automatically taking the reins from the mod wheel, following the connection of a controller. As with the ARGON, however, it’s very easy to adjust these parameters to your own personal taste.

For purposes such as organic sound design, sound effect-creation or moody soundscape building, an MPE approach is matchless. While waveforms and pre-shaped movement form the bedrock for Modal’s synth architecture, you’ll find that simply scaling your fingers up and down or left-to-right can concoct your own immediate organic sound shapes that sonically mirror your movements.

While these kinds of explanations of the potential sonics on offer are all well and good, it’s often best to see and hear a demonstration of MPE in practice. The below video demonstrates a KMI K-Board Pro 4 MPE control keyboard in use to manipulate the sound of a Modal 002R. Be sure to give it a watch. What’s immediately apparent is just how much every millimetre of hand and finger movement impacts on the output sound, just like a string instrument.

Saving The Note

If you’re looking for a new way to make and perform sound, or want to expand the full power of your Modal synth, then getting your hands on an MPE control surface and taking the leap into this world is undoubtedly something you should pursue. The rewards are limitless, particularly if you acquire something like the Artiphon 1 instrument – a guitar-like MPE string controller. This can reconfigure your entire approach to the world of synthesis, and spin it entirely on its head, as you strum and pluck at a wavetable.

But, while that more ‘out-there’ approach may not appeal to everyone, MPE needn’t be quite so daunting. The simple connection of a Keith McMillen K-Board Pro 4 or ROLI Seaboard to your SKULPTsynth, ARGON, COBALT or 00 Series synth is all you really need to begin swimming through those previously inaccessible dimensions of sound your synth is capable of producing. However you choose to apply the technology, it’s certain that MPE control will benefit musicians of all stripes, presenting a universe-sized level of performability.

All product and company names are trademarks or registered trademarks of their respective holders. Use of them does not imply any affiliation with or endorsement by them.

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