Developer Benjamin Dehli has introduced Overtonium, a free additive synthesizer plugin for Linux, Mac & Windows.

Overtonium approaches additive synthesis like a 32-channel mixer, with each channel representing a sine oscillator locked to a harmonic of the played note. Each partial has its own tuning, envelope, modulation, velocity, aftertouch, panning and level controls, while a separate noise channel provides additional non-pitched sound.

A central feature is the TUNE control, which continuously moves each partial between its equal-tempered position and its exact whole-number harmonic ratio. The instrument also separates this partial tuning system from keyboard temperament and inharmonic stretch, with six keyboard temperaments available: equal, just, Pythagorean, quarter-comma meantone, Werckmeister III and Young.

The instrument supports MPE, channel pressure and polyphonic aftertouch, along with per-partial pitch and amplitude modulation, random pitch drift, two-stage envelope behavior and global effects including wobble, tape echo and reverb. Twenty-eight presets are included.

Features:

• 32 sine-wave harmonic partials
• Separate noise channel
• 32 channel-style partial strips
• Individual tuning for every partial
• TUNE control that moves partials between equal temperament and just harmonic ratios
• Inharmonic STRETCH control
• Six keyboard temperaments
• Adjustable keyboard root and reference pitch from 415 to 466 Hz
• Keyboard tracking
• Per-partial phase control
• Per-partial pitch modulation with eight waveform shapes
• Per-partial amplitude modulation with seven waveform shapes
• Per-partial random pitch DRIFT
• Individual delay, attack, decay and sustain envelope controls
• Separate KEY OFF envelope
• Independent velocity response for every partial
• Independent aftertouch response for every partial
• Channel pressure and polyphonic aftertouch support
• MPE support
• Per-partial stereo panning
• Individual mute, solo and level controls
• Global WOBBLE effect
• Tape echo with two paths
• Global reverb
• Master level control
• Twenty-eight factory presets
• User preset saving and folder-based preset organization
• macOS, Windows and Linux support
• AGPLv3 open-source license

Pricing & Availability:

Overtonium is available now as free software under the GNU Affero General Public License v3. The complete source code is available through the project’s repository.