Surge (version 1.6.1.1 or newer shown above, running in Carla) is a cross-platform, realtime software sound synthesizer that was created by Claes Johanson in 2018, recently released into open source, and maintained by a group of volunteers. It is available for linux in the 64-bit architecture only.
Surge's synth engine provides two Scenes: Scene A and Scene B. Each of these Scenes is identical and includes: a Voice section which consists of three oscillators and a noise source; and Mixing section, a Filter Block and Gain/Pan controls. The Filter block includes an envelope generator for the filter and one for amplitude. Additional modulation capabilities are also provided which can be routed to various parts of the entire audio signal flow. (Modulated parameters are indicated in blue.) The modulation parameters are dedicated to either an individual voice or to the Scene. For example, key velocity and aftertouch are routed to the voice; pitch bend and the modulation wheel are routed to controlling the Scenes. There are also six LFO's for each voice, and 6 additional LFO's for modulating the Scenes.
Surge's GUI contains four sections: the Patch/Global section, the Scene Controls Section, the Modulation/Routing Section and the FX Section. The Patch/Global section allows to select whether to use just one Scene, "Single," or both Scenes "Split" along the keyboard or "Dual" and layered together across the entire keyboard. As an added function, when using Split or Dual mode, MIDI channel 1 and 4-16 will output both Scene signals, whereas MIDI channel 2 will output only Scene 1 and MIDI channel 3 will output only Scene 2. Preset browsing, loading and saving management is also done in this section.
The Scene Controls Section consists of two sub-sections: Sound Generation and Sound Shaping. Each individual oscillator has eight algorithms to choose from, each able to reproduce a series of waveforms: Classic, Wavetable, Window, Sine, FM2, FM3, SH Noise and Audio Input. The manual (link below) describes in detail the possibilities with each of the algorithms. Audio levels for all oscillators, noise and overall signal are also provided, as well as detuning, ring modulation, solo and mute buttons, and an "oscillator editor" section which allows to control detune spread, unison count and more. Polyphony (8-voice max) and three monophonic modes (retrigger, legato and fingered) are available.
Surge has two filters, each with 9 possible filter algorithms: LP12, LP24, HP12, HP24, BP, LP24L, Notch, Comb and Sample-and-Hold. Each of these filters offers additional subtypes (see manual at link below for more details). Control for the filter includes the Filterblock Configuration section, Filter Balance, Filter Keytracking and an ADSR-type envelope generator. In addition, there is an Oscillator FM Routing section and a Waveshaper section.
The Modulation/Routing Section is divided into three types: LFO's, voice/note properties and assignable controllers. The LFO's are equipped with DAHDSR-type envelope generators to allow for expression fluctuation in the LFO-modulated signal. Eight LFO wave shapes are provided, including an interesting "Envelope" waveform and a "StepSeq" waveform that can be drawn in a dedicated window. See the manual for additional details on assigning all the routing capabilities.
The FX section controls the effects management, and also allows to bypass the effects entirely. A "Character" section allows to choose between warm, neutral and bright. These settings will affect the amount of higher frequencies that are passed through. There is an Effect Block window that indicates the routing set-up of all activated effects. Again, see manual for further details.
For those using LibraZiK OS, you can download this Surge installation package until a (near-future) version is released that will address some incompatibility issues: Temporary Debian Surge Install Package. NB: It MAY OR MAY NOT work on other Debian-based systems. Recommended DAW: Carla.
Presets for Surge -A few initial presets I made for Surge. Rolling bank forthcoming. (Updated Sept. 08, 2019)
