AmSynth, created by Nick Dowell, uses the traditional subtractive synthesis approach to sound design, and can be run either as a standalone instrument or as a DSSI plug-in within a digital audio workstation such as Ardour or Qtractor.
AmSynth is a realtime, polyphonic/monophonic virtual synthesizer with touch-sensitivity. It includes two oscillators, each capable of generating several types of classic waveforms: the square wave can be modulated to reach a pulse wave, the triangle wave can be modulated to the point of a standard saw wave, and sine, noise and sample-and-hold waveforms are also provided. Oscillator 2 can be synced to oscillator 1, and it can also be detuned (finetuning to 4 semitones, semi-tones of 12 increments, positive and negative, and whole-octave detuning: down one or up two) to create broader and dissonant-type timbres. Syncing the oscillator and adjusting the semitone detuning gives some interesting FM-like timbres. An oscillator mix knob allows control of the balance between the two, and turning it all the way to the left or right will isolate the one or the other. Ring modulation is also provided.
A standard ADSR amplitude envelope controls the development of the audio level when a note is played, and the same ADSR structure is provided for the filter. The filter section includes 6 filters: low-pass, high-pass, bandpass filters, each at 12dB and 24dB.
An envelope strength knob controls the depth of the filter effect, and provides both positive and negative envelope possibilites. Resonance and cutoff are included in this section of the GUI as well.
AmSynth has one Low Frequency Oscillator. This LFO can be completely off, or affecting the pitch, filter and amplitude, or any combination of the three. Square, triangle, sine, sample-and-hold, saw-up, saw-down and noise waveform types are provided.
Together with the main volume and drive (distortion) controls, amSynth includes a plate-type reverb, a size knob to adjust wideness, stereo and damping knobs. Additional features of the newer version include mono/legato/poly control, and a very broad portamento capability. As of version 1.4.1, panning control is now also provided.
Another neat feature is the random function (sometimes called a "lazy button"). Using the ctrl+r keys, all controls are set to a randomly-assigned level. A kind of "evolution" mode, this function often produces uninteresting or unplayable sounds. But it sometimes produces some very interesting results. Many sounds I've made (from Bank 10 onwards) use this approach to soundmaking. Random setting selection is an ideal way to discover new sounds.
AmSynth has unlimited polyphony capability, although 16-note polyphony is usually sufficient. Pitchbend function can be selected in halfsteps, up to 2 octaves. I run amSynth through the Jack audio control, although Alsa also works well.
Using multiple instances of any softsynth is easy, and opens up limitless possibilties. My use of amSynth on debian-based versions of linux such as Ubuntu Studio (with KXStudio), antiX and BodhiLinux, has shown that multiple instances of amSynth (I haven't gone beyond 4 instances yet..) can be run simultaneously with less than 50% CPU usage on newer machines. Modulation and pitch bend, as well as any other external hardware Midi controller CCs you have at your disposal, can be assigned to different parameters for each instance. Portamento and polyphony can also be set for each instance, allowing for unique sonic control.
Where a single instance of amSynth provides two oscillators, running two instances will provide 4 oscillators; three instances will offer 6 oscillators, etc. (This is the way to get some very "fat" sounds.) It's easy to understand how a softsynth can quickly exceed the power of a traditional hardware synthesizer.
The important thing is to keep track of which instance you are modulating. For example, if a CC is set to modulate filter cutoff on instance one, and the pitch of the LFO on instance two, then modulating that CC will affect both parameters at the same time. Carefully choosing the control combinations of your midi controller's knobs and wheels will give you very powerful capabilities for both tweaking and live playing.
To get started, click on the menu bar and select "new instance" and a second interface will appear. If you are using Jack, check your Jack connections. Each new instance will be assigned a number after it. In the screetshots below, you will see three instances of amSynth, both in the midi window and audio window:
In the midi window above, the three amSynth instances are connected to the external Motif controller keyboard. In the audio window, the same three instances are connected to a Calf plugin effect, and that effect is connected to the system audio out. As I like to record using Audacity, connecting all three instances to Calf is handy, since Audacity will link to Calf and all three instances will be recorded. You could also, for example, open additional instances of Calf, and channel one instance through a delay, another through a reverb, and another through a chorus or flanger. The important thing is to have one "final" Calf instance that all the others will connect to. That will be the one that must be selected in Audacity.
As mentioned above, each instance can be independently linked to midi controllers. Each can have a different pitch bend range and of course, different settings. The first thing to check is the volume level of each instance. Having each instance set to maximum volume will result in unpleasant distortion, so as a rule, consider that all volumes should total to one hundred: with two instances, put both volumes to 50 percent; with three instances, put all volumes to about 30 percent; with four instances, put each volume level to 25 percent. Of course, some patches are naturally louder than others, so further adjustment may be needed to get the right balance. Each voice must be loaded in order to hear the final sound correctly. For example, the patch "Space Concert" has three voices in it. In the bank, they will be listed as "Space Concert01," SpaceConcert02" and "SpaceConcert03." So three instances must be opened in order to play this sound. Remember to make sure all instances are connected to both your midi controller and the audio line!
For use with multiple instances: MixedBag 1
amSynth (version 1.4.2) amSynth is now officially at version 1.4.2 (screenshot on this page is version 1.4.0).