Surge

“SURGE is a free, open source synth that’s available for macOS, Windows & Linux.

The software synth is described as a ‘subtractive hybrid’ design.

Each patch contain two ‘scenes’ which are separate instances of the entire synthesis engine (except effects) that can be used for layering or split patches.

Quick category-based patch browser

Runs on a variety of operating systems, plugin formats, and architectures

Factory Sounds

1725 patches

523 wavetables

Key Features:

• 3 oscillators per voice
• 8 versatile oscillator algorithms: Classic, Sine, Wavetable, Window, FM2, FM3, S/H Noise and Audio input
• Most algorithms (except FM2, FM3, Sine and Audio-input) offer up to 16-voice unison at the oscillator level.
• Oscillator FM/ring modulation
• Noise generator with variable spectrum.
• Two filter units in 8 different configurations
• Available filter algorithms: LP12 (3 variations), LP24 (3 variations), LP Ladder (1-4 poles), HP12 (3 variations), HP24 (3 variations), BP (4 variations), Notch (2 variations), Comb (4 variations), S&H
• Waveshaper (5 shapes)
• Modulation
  • 12 LFO units available, 6 are per voice and 6 are global for the whole scene
  • DAHDSR envelope generators on every LFO-unit
  • 7 deformable LFO waveforms + drawable/step sequencer waveform
  • LFO 1 allows envelope retriggering when used as step sequencer
  • Extremely fast and flexible modulation routing. Almost every continuous parameter can be modulated.
• Effects
  • 8 effect units arranged as 2 inserts per scene, 2 sends and 2 master effects
  • 10 top-quality algorithms:
  • Delay, Reverb, Chorus, Phaser, EQ, Distortion, Conditioner (EQ, stereo-image control, and limiter), Rotary speaker, Frequency shifter, Vocoder”

Source : synthtopia.com