Playing Reaktor ensembles is useful. Building one teaches you how synthesis really works, because nothing happens unless you connect it yourself. This chapter builds a simple subtractive synth in Reaktor's Primary level - the same architecture you learned in the subtractive chapters, wired by hand.
Start a new ensemble
Create a new ensemble and add a new, empty instrument. Open its Structure view. You will see the instrument's audio outputs; everything else you add yourself. Right-click in the structure to insert modules from the menu.
The signal flow
The synth follows the classic path:
MIDI note and gate → oscillators → mixer → filter → amplifier (with envelope) → output
MIDI inputs
Two modules bring MIDI into the structure:
- Note Pitch - outputs the pitch of the note played. Connect it to the pitch input of your oscillators so they play the right notes.
- Gate - outputs a signal while a key is held, with a value based on velocity. Connect it to your envelopes so they start when a note is pressed and release when it is let go.
Oscillators
Insert two oscillator modules - a sawtooth and a pulse, for example. Connect Note Pitch to each oscillator's pitch input. To detune the second oscillator, add a constant or a knob to its pitch with an add module, so you can offset it by a few semitones or a fraction of one.
Mixing
Use an amplifier/mixer module, or add modules, to combine the oscillators. Add knobs for each oscillator's level. Knobs created in the structure appear automatically on the panel.
The filter
Insert a filter module - a multimode filter with low-pass output is a good start. Connect the mixer output to the filter input. Add knobs for cutoff and resonance and connect them to the filter's controls.
Envelopes
Insert two ADSR envelope modules:
- Amp envelope - connect the Gate to its gate input, and its output to an amplifier module placed after the filter. Now notes start and stop.
- Filter envelope - connect the Gate to it too, and add its output (scaled by an amount knob) to the cutoff, so the filter moves with each note.
Add knobs for attack, decay, sustain and release on each.
Output
Connect the amplifier's output to the instrument's audio outputs. Play a note. If you hear nothing, follow the signal path from MIDI to output and check every connection - nothing in Reaktor happens by default.
Polyphony
Set the instrument's number of voices in its properties. More voices let you play chords; one voice makes it monophonic. Reaktor processes each voice separately until signals are mixed down - which is why some modules have voice-combining options.
Arrange the panel
Switch to the Panel view. Arrange the knobs into sections - oscillators, filter, envelopes - and label them. A clear panel makes an instrument usable.
Save
Save the ensemble, and create a few snapshots - a bass, a pad, a pluck - to show what your synth can do.
Going further
Once the basic synth works, try adding:
- An LFO routed to cutoff or pitch.
- A noise oscillator.
- Glide, by smoothing the Note Pitch signal.
- Velocity to filter cutoff.
- A simple effect - a delay or chorus - after the amplifier.
Do this now
- Build the two-oscillator synth above, step by step.
- Make it play in tune and respond to the gate.
- Add a filter envelope with an amount knob.
- Save three snapshots: a bass, a pad and a pluck.