Surge is a super versatile synth with a bunch of sound presets for the user who just like to browse sounds and complete in-depth editing possibilities for sound designers.

Previously released by Vember Audio and open sourced in September of 2018, Surge is now supported by a community of volunteer open source developers, designers, testers, musicians, synthesizer enthusiasts, and content creators.
For more detailed info on Surge or the team behind it, check out https://surge-synthesizer.github.io/

Surge manual

Wiki

GENERAL:

• Synthesis method: Subtractive hybrid
• Zoom function to make Surge fit your screen
• 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
• MPE compatible

FACTORY SOUNDS:

• 1010 patches
• 183 wavetables

OSCILLATORS

• 3 oscillators per voice
• 8 versatile oscillator algorithms

FILTER

• 2 filter units in 8 different configurations
• Feedback loop
• 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

MODULATION

• 12 LFO units available, 6 are per voice and 6 are global for the whole scene
• DAHDSR envelope generators on every LFO-unit
• 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 fx
• Delay, Reverb, Chorus, Phaser, EQ, Distortion, Conditioner (EQ, stereo-image control, and limiter), Rotary speaker, Frequency shifter, Vocoder