(musTh625) absynth synthesis tips

Coming up with interesting analog synthesis instruments takes some practice and experimentation. To get you started, I’m outlining a basic work procedure. As you get more experienced, you can make changes to this process and try more techniques.

basic outline

At the very beginning, start with a new sound (File > New Sound). This brings up a single oscillator using a sine wave as its source. From there (in Patch view):

  1. Start with an interesting sound source generator.
  2. Apply a filter (or some other process).
  3. Add envelopes and LFO modulation to synthesis parameters.
  4. Add external performance controls via MIDI tab
  5. Add additional branches (B and C)

Now to go a little deeper.

start with an interesting sound source generator

At the top of any synthesis chain in Absynth (or any other synthesis program) is a sound generator. Typically, these generators take the form of oscillators, and Absynth uses the abbreviation OscA (and OscB, OscC). Absynth has a flexible generator that can go from a single oscillator, to modulation, to samples, to live audio input. Let’s start with the Single oscillator type, which has a selectable waveform.

Focus on the elemental waveforms (sine, triangle, square, sawtooth, noise) and their filtered variants. The inharmonic waveforms can be of use as well. In the beginning it will be easier to start with a wave rich in frequency content (anything but a sine, and less likely to be a triangle). With a rich sound source, you can apply filtering with modulation to get interesting results. Try selecting the different elemental waveforms to hear the difference between them.

apply a filter

Filters provide a way of boosting and cutting the amplitude of specified frequency ranges, which can alter the timbre of the sound over time. Click on the left-edge title bar to add a filter to the synthesis chain. The default filter is a LPF 2 Pole, which stands for Low Pass Filter with a two sample filter delay, providing for a 12 dB per octave slope after the cutoff frequency. More poles (4 and 8) provide a steeper response slope (24 dB and 48 dB per octave, respectively). Stick to the filters with the pole designations for a more analog style design and sound.

Adjust the filter frequency and resonance controls. Start with the filter frequency. Sweep the cutoff frequency up and down to hear how the sound can brighten and darken. Now add varying amounts of resonance and do the filter frequency sweep again. The more resonance you have, the more amplitude boost you get at the cutoff frequency. That boost can give you a sense of cycling through the partials/overtones, as a partial will jump out when the cutoff frequency sweeps past it. Try LPF’s with additional poles.

Always be listening to the result of these manual controls. Any parameter you can change in the patch window can be automated through the use of envelopes, LFOs, and MIDI performance controls.

add envelopes and LFO modulations to synthesis parameters

Once you have experimented with manual changes to filter settings, start adding and editing envelopes. Switch to the Envelope view. If you command-click on the Envelope tab, the envelope window will pop out as a separate window. You can do with with any window.

When you create a new sound, Absynth provides initial ADSR amplitude envelopes for oscillators A, B, and C (whether your have all three oscillators active or not). You can drag breakpoints to lengthen/shorten attack, initial decay, and release times. You can also adjust the sustain level. To create the impression of a short, accented attack, you should drop the sustain level -6 to -12 dB below the attack level. For sounds that fade in, or have legato attacks, your sustain level will usually be the same as your ending attack level.

Add envelopes to control filter cutoff frequency, and maybe resonance. A good thing to start with for filter frequency is to copy your amplitude envelope and paste in into the filter frequency envelope. Brightness and amplitude usually track together, or in related ways. Your envelope for filter frequency will be a percentage of whatever value you specify in the patch. For example, if your cutoff frequency is specified at 10,000 Hz, then the maximum value for the filter frequency envelope will be 10,000 Hz. If you set your sustain level lower than maximum, the filter frequency will be lower than 10,000. You can click on a breakpoint in the envelope to see the frequency value at that point. You don’t have to start at 20 hz, nor do you have to move to the maximum amount you set in your patch.

You can experiment with having your filter decay faster than your envelope, or fade in slower than your envelope, for different effects. You can also link the filter envelope to the amplitude envelope for that oscillator (or anything else), so that you only have to edit one envelope to change both.

In addition to envelopes, you can apply LFO (Low Frequency Oscillators) to any parameter of your patch. Try applying an LFO to channel pitch, oscillator amplitude, filter frequency, or filter resonance. You specify LFOs through the LFO tab. You can choose a waveform (noise waveforms have a random quality). To hear the effect of the LFO, you select the channel (A, B, C) of any parameter you want to modulate, and set the amount of modulation. Any modulation will be a reduction in the max amount, except for pitch, which will oscillate above and below.

Specifying the frequency of the LFO is backwards from how you specify frequency of a filter cutoff. Absynth thinks in terms of the duration of one cycle of the LFO, which is quite useful for creating rhythmic effects (you can specify duration in seconds or beats, but beats only works within a DAW host like DP). To make an LFO oscillate faster, you must make the duration value less. A 1 second duration is 1 Hz; a 0.5 second duration is 2 Hz, etc.

add external performance controls

You add MIDI controls in the Performance tab. Within this tab, there are three important sub-tabs: Controllers, Assignments, and MIDI.

Start with the MIDI sub-tab. You assign key velocity to control synthesis parameters from within this sub-tab. Start by assigning velocity to control Oscillator amplitudes. You can experiment by having it control one oscillator more than another. Next, consider assigning velocity to modulate filter cutoff frequency, as sounds tend to get brighter when they get louder. You can also control Modulation Index if you are using FM synthesis.

It can interesting to try using velocity on less obvious parameters, like LFO frequency. You could control LFO frequency with velocity, and invert the mapping depending on how you want frequency to respond.

The MIDI sub-tab also allows you to set your pitch bend range, and assign a controller to volume and pan (typically 7 and 10).

Move to the Controllers sub-tab. Here you will find 12 Macro controls, along with the modulation wheel, channel volume, and pan. You assign an external MIDI CC to macro controls. You can do this by using the Learn function for each macro control. I generally set these to match the controller I’m using. You have to set them for each saved voice.

Finally, move to the Assignments sub0-tab. You use the assignments sub-tab to assign macro controls to various synthesis parameters. Select a macro control from the list on the left, and the choose add to have it control a synthesis parameter. You control how much change a source applies, etc. You can have one macro control affect multiple synthesis parameters. Once you assign a macro control, the name of the control changes to match the first parameter to which it is assigned. It will still show the MIDI CC number of the control.

adding additional channels

(next post)


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