Additive synthesis has always had a reputation problem. It is the most transparent synthesis method there is — build any sound from sine waves — and also the one most likely to hand you a spreadsheet of 512 partials and wish you luck. Melatonin has spent more than six years trying to solve that, and Sine Machine is the result: an additive synth built around visual feedback rather than numeric tables, now out of early access for macOS, Windows and Linux.

The headline number is up to 10,000 time-domain oscillators. The more interesting number, for anyone reading this site, is one: the number of MIDI channels an ordinary synth gives each note. Sine Machine now supports MPE, and additive synthesis turns out to be one of the most rewarding places to send per-note expression data.

Why additive and MPE fit together

Most synth architectures give you a small number of macro handles — filter cutoff, oscillator morph, an FM index. MPE feeds pressure, slide (CC74) and per-note pitch bend into those handles, and the sound moves in the way the designer anticipated.

Additive is different. Every partial is an independent voice with its own amplitude envelope, its own pitch, its own behaviour over time. Sine Machine exposes individual partial ratios, per-harmonic ADSRs, and per-harmonic pitch, glide and tremolo. Point a pressure signal at a spectral tilt across that harmonic stack and you are not opening a filter — you are physically rebalancing the timbre, the way pressing harder on a real string or reed does.

That is the reason acoustic instruments are hard to fake with subtractive synthesis. A louder clarinet note is not a quieter clarinet note with the filter opened; it has a different harmonic recipe. Additive plus MPE gets you closer to that relationship than almost anything short of physical modelling.

The visual approach

Sine Machine's pitch is that it is a friendly starting point for additive synthesis, and the way it delivers that is colourful real-time visualisers showing what each partial is doing as you play. This matters more with an expressive controller than without one.

When you play an Osmose, a Seaboard, a Continuum or a LinnStrument, you generate a continuous stream of three-dimensional data per note. Without visual feedback, diagnosing "why does this patch sound smeared when I press hard" is guesswork. With a live spectral display, you can see the partials fighting each other. It is the same argument behind dedicated tools like MPE Insight — expression data is easier to shape when you can see it.

MTS-ESP is the quiet second headline

Sine Machine also supports MTS-ESP, ODDSound's microtuning standard. For additive players this is not a niche extra. If you are already specifying partial ratios by hand, you are already thinking in just intonation, and MTS-ESP lets the whole session follow a shared tuning table rather than each plugin being retuned individually.

Be aware that MPE and MTS-ESP both use pitch bend, and they can collide. If notes drift out of tune when you use both, the usual culprit is a pitch-bend curve or range mismatch rather than a bug in either system — worth checking before you file a support ticket.

Practical notes

Sine Machine ships as VST3, AU and CLAP, with no VST2 build. The CLAP version is the interesting one for expressive players: CLAP's note-expression system carries per-note data natively rather than encoding it as pitch bend across channels, which sidesteps a whole category of channel-rotation problems. Hosts like Bitwig Studio and Reaper support it today.

Pricing starts at $60, with a free 14-day demo available from the Melatonin site. That is unusually accessible for a synth in this category — additive instruments have historically sat at the premium end.

Is it worth your time?

If you own an MPE controller and your patch library is mostly wavetable and subtractive, Sine Machine is a genuinely different flavour of expression. Pressure that redistributes energy across a harmonic stack sounds unlike pressure that opens a filter, and the difference is obvious within about thirty seconds of playing.

If you have bounced off additive synthesis before, the visualisers are the actual product here. Ten thousand oscillators are only useful if you can tell what they are doing.

Sources: Melatonin, SYNTH ANATOMY, rekkerd