The Expressiv Infinity MIDI Guitar

Do you remember the Synthaxe? It was an incredible, super expensive piece of gear from 1980s that allowed guitar players to control synthesisers directly over MIDI.

Featuring a vibrato bar, strings for plucking and keys for pressing, the SynthAxe was incredibly ahead of its time, allowing guitarists to get rid of latency problems that are typical of pitch-to-midi systems (Roland GK pickups all have this major problem) and thus enabling true expressive control over the music you played.

The SynthAxe was purely a controller – it did not have onboard sounds.

A complete SynthAxe system cost over £10,000 and only several were made. The late and great Allan Holdsworth was the main advocate of the instrument, even featuring it on the cover of the incredible “Atavachron” album.

When SynthAxe systems pop up on eBay they change hands for well over €25.000!



Although very 30+ years old in design, the features of the Synthaxe are still advanced as of today.
However, now we have much much smaller, infinitely more powerful and affordable processors (DSPs) that allow similar features to be enclosed in a more consumer-friendly package.

Meet the Rob O Reilly Expressiv Infinity Guitar

EXpressiv Infinity Guitar

The Expressiv infinity combines:

  • The features of a standard electric guitar (with 2 magnetic single coils) you can jack to a standard amplifier
  • A direct MIDI output in the standard 5 pin format (so it’s compatible with any standard MIDI instruments such synths and pianos without any further conversion stages as happens with Roland GK-based systems)
  • An onboard dedicated processor for pitch-to-MIDI conversion, allowing for very fast and accurate tracking, virtually eliminating the latency problems typically associated with guitar synth technology.
  • USB connectivity
  • a cleverly positioned, body installed X-Y pad allowing for extra expressivity over the standard string plucking/picking. It’s located under one of the pickups and you can operate it with your hand or even with a pick to create expression, modulate filters and LFOs of your synths to bring your performance alive.
  • Full poliphony.

See the demos below:


The instrument has a unique design – and feature set – which sets it apart from traditional guitars.

To people like me, the instrument looks quite exciting and attractive. The price tag is around the €1500 mark – not cheap, not super affordable, but doable if you’re serious about experimenting with sounds.

Now that may be distinctive, but considering how conservative the typical guitar player is, that may well be something damaging the popularity of the Xpressiv guitars. Rob O reilly also produces a second, more traditionally inspired two humbuckers guitar he calls the Midi Pro Guitar, coming in at a heftier price tag (almost €2k).

Tech specs

Xpressiv Infinity specs

As you can see in the diagram above, the whole system is very thoroughly thought.

The joystick, especially, is a killer feature. It combines program change, control change and pitch bend in a single device. 

On the top of the guitar you also have a kill switch, MIDI volume, guitar volume and magnetic pickup selection.

The Expressiv Infinity looks like a very carefully made system for removing the frustration from playing synths (and more) with a guitar, and makes me want to experiment with guitar synths again. 
Do you share the same feeling? 🙂



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