Melatonin Sine Machine is a friendly additive synthesizer built to make one of synthesis's most intimidating techniques enjoyable. Additive synthesis creates sound by summing many sine waves, one per harmonic, which is how acoustic instruments actually behave. It excels at organic, evolving tones, but it has always been fiddly to control. Sine Machine solves that with a visual, zero-knob interface layered over a serious engine: 20 voices of 511 time-domain oscillators, more than 10,000 in total, plus over 20,000 LFOs.
Rather than editing harmonics one by one, you shape them in bulk. Per-harmonic ADSR, volume, and pitch LFO are all editable across the partial series in a single gesture, and animated visualizers show exactly what each partial is doing. Two effects are rendered the additive way: a reverb built from 1,000 sine waves, and additive brickwall and Gaussian band-pass filters that carve the harmonic content directly. Per-harmonic Gaussian pitch noise and absolute pitch glide add the organic instability that makes acoustic sound feel alive, while mappable partials open inharmonic, bell-like, and metallic timbres.
Expression and tuning are strong out of the box, with MPE support and MTS-ESP microtuning, features usually reserved for high-end instruments. More than 140 factory presets ship as hackable plaintext JSON, so you can read and learn from any sound. The trade-offs are honest: there is no AAX build, the additive character leans organic rather than aggressive, and the unconventional workflow takes time to click. Producers who prefer a conventional subtractive path should look at Vital or the free Surge XT.
Sine Machine is pay-what-you-want, with a suggested price around $75, sold only through the official Melatonin site. Read the full Sine Machine review, or browse other synths at Plugin Boutique.