SCHLAPPI ENGINEERING Three Body Triple Digital FM PM Oscillator
The Three Body is a phase and frequency modulation toolkit, designed to bring digital techniques to an analog interface. It consists of three oscillators which can be used independently but which have normalised connections to facilitate exploration and improvisation.
Controls
Controls affected by the FREE/RATIO state, works the same for each oscillator.
| CONTROL | FREE | RATIO |
| COARSE/MULT | Coarse pitch control | Tracking multiplier |
| FINE/DIV | Fine pitch control | Tracking divider |
Modulation controls are the same for the outer oscillators, but the inner oscillator has an extra phase input and index control (VCAs) on phase modulation instead of frequency
| CONTROL | DESCRIPTION | Oscillato r |
| PHASE CV | Attenuator over phase input | outer |
| PHASE INDEX 1 | Attenutor for CV control over amount of phase input 1 | inner |
| PHASE INDEX 2 | Attenutor for CV control over amount of phase input 2 | inner |
| FM CV | Attenuator for amount of FM input | inner |
| FM INDEX | Attenuator for CV control over amount of phase input | outer |
Outputs – All outputs are bipolar, 10V peak to peak, and affected by the phase or frequency modulation of the related oscillator.
| LABEL | NAME | DESCRIPTION | ||
| SINE | Sine wave output, modulation adding to the phase | |||
| COSINE | Cosine output, 90 degrees offset ahead of sine output with modulation subtracting from the phase. center oscillator only | |||
| TRIANGLE | Triangle wave output | |||
| SAW | Saw wave output | |||
| COSAW | Saw wave 90 degrees offset ahead of saw output with modulation subtracting from the phase. center oscillator only | |||
| SQUARE | Square wave output | |||
Inputs – Inputs affected by the FREE/RATIO state, works the same for each oscillator
| INPUT | FREE | RATIO | notes |
| TRANSPOSE | Global Volts per octave input, adds to all oscillators pitch | Has no effect | Affects all oscillators in free mode, including those in LFO mode |
| VOCT/RATIO | Volts per octave input | CV adding to multiplier or divider | Bipolar, can be used at audio rate |
| SYNC | Hard sync | Tracking input | threshold at 1V, tracks on rising edge |
Modulation inputs are the same for the outer oscillators, but the inner oscillator has an extra phase input and index control (VCAs) on phase modulation instead of frequency
| INPUT | RATIO | |
| PHASE | Phase input, breaks internal normalization | |
| PHASE INDEX | CV control over amount of phase, breaks normalization to 10V | Outer osc |
| FM | Frequency modulation input, expo or lin, breaks internal normalisation | |
| FM INDEX | CV control over amount of phase, breaks normalization to 10V | Inner osc |
States
The heart of the three body is a digital logic state machine with 8 states (per oscillator) defined by three switches (per oscillator). This determines whether the oscillator is free, operating much like an analog oscillator, or tracking in a ratio mode as is necessary for Chowning style digital FM. It also determines the behavior of the VOCT/RATIO CV, frequency modulation, and sync inputs.
| FREE/RATIO | EXPO/LIN | LOW/HIGH/DIV/ MULT | DESCRIPTION |
| FREE | EXPO | LOW | LFO with exponential frequency modulation |
| FREE | EXPO | HIGH | VCO with exponential frequency modulation |
| FREE | LIN | LOW | LFO with linear frequency modulation |
| FREE | LIN | HIGH | VCO with linear frequency modulation |
| RATIO | PHASE | DIV | Tracking oscillator with phase modulation and CV over division |
| RATIO | PHASE | MULT | Tracking oscillator with phase modulation and CV over multiplication |
| RATIO | LIN | DIV | Tracking oscillator with linear frequency modulation and CV over division |
| RATIO | LIN | MULT | Tracking oscillator with linear frequency modulation and CV over multiplication |
Recommended Starting Patches
Rhythmic creaks:
- Set center oscillator to FREE, LOW
- Outer oscillators to RATIO or FREE, LOW
- Listen to the center oscillators sine and cosine outputs as a stereo voice
- turn PHASE INDEX 1 and 2 all the way up
- Slowly turn up turning up the PHASE CV controls on the outer oscillators
- Experiment with the FM indexes and modes
Arpeggiation:
- Set center oscillator to FREE, HIGH
- Outer oscillators to RATIO, HIGH
- Turn all modulation indexes down
- Listen to the outer oscillators as a stereo voice
- Experiment with the ratio controls
- Send LFO or envelope CV to the VOCT/RATIO inputs of the outer oscillators
- Try using the SAW and COSAW outputs as a stereo output pair
Chords:
- Turn down all modulation
- Mix together and listen to sine or triangle outputs of all three oscillators
- Send Pitch CV to TRANSPOSE input
- Explore the modes, start turning up cross modulation
Stereo phase modulated oscillator:
- Set center oscillator to FREE, HIGH
- Outer oscillators to RATIO
- Listen to the center oscillators sine and cosine outputs as a stereo voice
- turn PHASE INDEX 1 and 2 all the way up
- modulate PHASE 1 INDEX and PHASE 2 INDEX with envelopes.
- Experiment with the modes of the outer oscillators
- Try using the SAW and COSAW outputs as a stereo output pair
Dubstep bass:
- Set center oscillator to FREE, HIGH
- Left oscillator to RATIO
- Listen to the center oscillator
- PHASE INDEX 1 all the way up
- Patch a clock into left SYNC input
- Send a slow tempo related CV to the left VOCT/RATIO input
- Experiment with cross modulating between the left and right oscillators
Some tips:
- Phase modulate with the modulator a higher frequency than the carrier
- Frequency modulate with the modulator a lower frequency than the carrier
- Start with all cv and indexes down
- Keep cross modulation low unless extremely noisy sounds are desired
Schlappi Engineering – schlappiengineering
