Issue 93


Ableton Live 12
What’s in. What’s out. What to expect.


Vember Audio/Surge Synthesiser: Surge XT

A free and open-source hybrid synthesiser.


4 December 2023

Surge XT (extended) began its life as a Vember Audio product, but when Claes Johanson became too busy with other projects, the software synth was open-sourced on GitHub. It is a fully featured VST sampler, with a heavy focus on synth. Featuring many synthesis techniques, a great selection of filters, a flexible modulation engine, a smorgasbord of effects, and modern features like MPE and micro-tuning, the Surge XT is a powerful creative tool. 



Synthesis method: Subtractive hybrid. Each patch contains two scenes which are separate instances of the entire synthesis engine (except effects) that can be used to create layered or split patches. There is a quick category-based patch browser with textual search and favourites, and it runs on a variety of operating systems, plugin formats, and architectures.

Factory Sounds
  • Over 2800 patches
  • Over 700 wavetables

Surge XT has three oscillators per scene, with 12 versatile oscillator algorithms; Classic, Modern, Wavetable, Window, Sine, FM2, FM3, String, Twist, Alias, S&H Noise, and Audio Input. 

‘Classic’ oscillator is a morphable pulse/saw/dual saw oscillator with a sub-oscillator and hard sync. ‘Modern’ oscillator is a mixable saw/pulse/triangle oscillator with an optional sub-oscillator mode for triangle (which can also change to sine or square) and hard sync. ‘FM2/FM3’ oscillators consist of a carrier and 2 or 3 modulators and various options. ‘String’ oscillator uses two filtered waveguides to emulate plucked or bowed string sounds. ‘Twist’ oscillator is based on a very famous Eurorack macro oscillator, and it offers a myriad of synthesis options in a very simple and quick way.

Most algorithms (except FM2, FM3, Twist and Audio Input) offer up to 16-voice unison at the oscillator level. Oscillator FM in three different configurations and ring modulation between oscillators 1-2 and 2-3. Most oscillator algorithms (except FM2, FM3, Sine and Alias) are strictly band-limited, yet still cover the entire audible spectrum, delivering a clear, punchy and clean sound. Noise generator with variable spectrum (available directly in the oscillator mixer).

Filter Block

There are two filter units in eight different configurations, with feedback loop available in seven of them. 

Filter Algorithms:
  • Lowpass (12 and 24 dB/oct, each with 3 variations)
  • Legacy Ladder Lowpass (6-24 dB/oct)
  • Vintage Ladder Lowpass (2 variations, each with and without gain compensation)
  • Highpass (12 and 24 dB/oct, each with 3 variations)
  • Bandpass (12 and 24 dB/oct, each with 3 variations)
  • Notch (12 and 24 dB/oct, each with 2 variations)
  • Allpass (3 variations)
  • Comb (positive and negative)
  • S&H
Open-source additions to the filter algorithms include: 
  • K35 and Diode Ladder filter types from Odin 2 synthesizer
  • 12 and 24 dB/oct multimode filters from OB-Xd
  • The weird but fascinating Cutoff Warp, Resonance Warp and Tri-Pole filters by Jatin Chowdhury
  • Filters can self-oscillate (with excitation) and respond amazingly fast to cutoff frequency changes and there are 43 Waveshaper shapes.

12 LFO units are available, six are per voice, and six are global for the whole scene — with DAHDSR envelope generators on every LFO. LFO shapes consist of seven deformable LFO waveforms, step sequencer, a fully-fledged multi-segment envelope generator (MSEG) with various curves and up to 128 nodes, and last but not the least a formula modulator which utilises Lua scripting language to provide completely custom modulator output. Voice LFOs allow envelope re-triggering in step sequencer mode. Extremely fast and flexible modulation routing is possible and almost every continuous parameter can be modulated.


16 effect units are available, arranged as 4 inserts per scene, 4 sends, and 4 master effects. There are 27 unique effect algorithms grouped into 6 categories.

  • 3-band fully parametric EQ
  • 11-band graphic EQ
  • Exciter
  • Resonator
  • CHOW
  • Distortion
  • Neuron
  • Tape (based on ChowTapeModel!)
  • Waveshaper
  • Combulator
  • Frequency Shifter
  • Nimbus
  • Ring Modulator
  • Treemonster
  • Vocoder
  • Chorus
  • Ensemble
  • Flanger
  • Phaser
  • Rotary Speaker
Time & Space:
  • Delay
  • Reverb 1
  • Reverb 2
  • Spring Reverb
  • Airwindows (itself containing 56 effects)
  • Conditioner
  • Mid-Side Tool

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Issue 93


Ableton Live 12
What’s in. What’s out. What to expect.