PLICATA is a patchable monophonic software synthesizer for iPhone and iPad combining a morphing oscillator, CV modulation, microtonal performance and a 32-step arpeggiator.
Four features, and the combination of the first and third is more interesting than either alone.
Why a touchscreen is the right home for microtonality
The practical obstacle to playing microtonal music has never been theory. It is that the instruments are built for twelve notes per octave.
A piano keyboard is a physical commitment to 12-tone equal temperament. You can retune the sound engine underneath it — our microtonal primer covers how, with Scala files and MTS-ESP — but you are still playing a layout designed for a different tuning. In 31-TET you have 31 pitches and 12 keys per octave, so the mapping is arbitrary and nothing is where your hands expect.
The serious hardware answers are isomorphic keyboards — the Lumatone, the Striso, the Linnstrument — where the physical layout follows the tuning’s structure rather than a historical compromise. They work beautifully and they cost between several hundred and several thousand pounds.
A touchscreen has no fixed layout at all. It can present whatever arrangement a tuning implies, change it per scale, show pitch continuously, and give you an interface that is correct for 19-TET and then correct for 53-TET a moment later. The hardware cost is a phone you already own.
That is a genuine structural advantage, and it is under-exploited. Most iOS synths put a piano keyboard on the glass — reproducing the constraint for familiarity’s sake.
Patching on glass, which works better than it should
“Patchable” on a phone sounds like a compromise and it is one of the things touch interfaces are actually good at.
Dragging a connection from an output to an input is a direct gesture. It is arguably more direct than a physical patch cable, where your hand obscures the panel and you are feeling for a 3.5mm jack. On a screen the connection is visible as a line and the routing is legible at a glance.
What you lose is the thing modular people value most: tactile, simultaneous, eyes-free control. You cannot grab three knobs at once on a touchscreen, and you cannot find a control by feel. For performance that is a real limit.
So the sensible read of PLICATA is that it is strong where glass is strong — exploring a patch, and playing pitch — and weaker where hardware is strong, which is physical manipulation while playing.
The morphing oscillator and the microtonal engine are the pairing that matters
Here is the part worth dwelling on, because it connects to something we have written about twice in a fortnight.
Consonance is a property of spectra, not of ratios in the abstract. Two tones sound rough when their partials fall close enough to beat. Which means the tuning that sounds consonant depends on the timbre you are playing it with — the central argument of Sethares’ Tuning, Timbre, Spectrum, Scale, and the mechanism behind Harmonic Eigenspace’s map of chord consonance and behind BLOT’s shape-as-patch modal synthesis.
A morphing oscillator changes its spectrum continuously. A microtonal engine changes its tuning. Putting both in one instrument means you can move through the space where tuning and timbre are matched — finding the spectrum at which a given scale locks in, rather than accepting whichever consonances a fixed waveform happens to produce.
That is the most interesting thing you can do with microtonality and almost no instrument makes it easy, because tuning and oscillator design normally live in different parts of the signal path and different parts of the interface.
Monophonic is the honest limitation. Microtonal harmony is where most of the theory lives, and a single voice gives you melody and arpeggiated implication rather than chords. The 32-step arpeggiator is presumably the answer to that, and an arpeggio in just intonation does carry harmonic information — but it is not the same as four voices sounding together.
What to try first
Pick one non-12 tuning and stay in it. 19-TET or 31-TET, per our primer’s advice. Both have better thirds than 12-TET and still behave like a tuning system rather than a continuum.
Then sweep the oscillator morph while holding an interval. You are listening for the point where the beating stops. That point is where the timbre’s partials align with the tuning’s ratios, and it is a thing you can hear immediately once you are listening for it.
And use the arpeggiator to imply harmony. A monophonic instrument in a tuning with a pure 7:4 can state a harmonic seventh chord as an arpeggio, and the consonance is audible even sequentially.