1 Introduction TiaR c-x-f synth rev 09 complex X filter synthesizer A brief user guide by Thierry Rochebois The cxf synthesizer is a jsfx software synthesizer designed for Reaper. It can be downloaded from the Reaper Stash as a zip. The zip file must be unzipped in reapers effects folder (typically something like C:\Users\User\AppData\Roaming\REAPER\Effects on a PC under win7). The complex X filter synthesizer is a mono synthesizer based on an unusual kind of "filter". The "complex X filter" is a nonlinear filtering device that filters and phase-distorts sounds. Even a simple sine wave can induce a wide range of sounds. The "complex X filter" is quite complicated to set and trimming/tuning it can be tedious... So I made a unit with many presets. This reduces the number of sliders and simplifies its operation. To add dynamics and variations, you can choose two presets and morph between them (with a modulation source such as the modulation wheel, a LFO or an envelope). The audio path of the c-x-f synthesizer consists in: - a pair of sine-wave generators (with detuning and modulated mix), - a complex X filter (with presets & morphing, pitch modulation and resonance modulation), - a ring modulator (for square like sounds and weird bending effects). The built-in oscilloscope will be helpful for understanding what's going on. The c-x-f synthesizer can be used as a MIDI controlled effect: the internal sine-wave generators can be replaced by the external input. So, you can chain your favorite VST-i and the c-x-f synthesizer. Polyphony can be achieved by stacking c-x-f synthesizers in a particular mode (see Polyphony by MIDI stacking).
2 Features ~1.7% CPU on Intel i5-4440 2 ADSR - 17 presets (one slider/selector per ADSR) - velocity and expression sensitive - time factor/velocity sensitivity Oscillators - cos/sin quadrature oscillators - one auxiliary oscillator - ratio (over or sub tone -> enhances the distortion effect) - beating detune (fixed frequency offset -> pad/phasing effect) - modulated mix (15 selectable modulation sources) External input - can be used as a MIDI controlled effect. - select Auxiliary Osc Ratio / Source to: - External: the external signal is processed by the c-x-filter. - Ring mod External: the external signal is ring modulated and processed by the c-x-filter. c-x-filter - 16 presets (including noise modulated presets). - "morphing" between two presets - 15 modulation sources available for "morphing". - Complex valued resonator - stability - modulation robustness (even with audio-rate noise modulation) - Nonlinear audio-rate modulations - Four point control (diamond angle) - Forward pitch modulation (based on input signal), produces swept ringing. - Fed-back pitch modulation (based on internal state), produces lots of harmonics. - all of these are defined in the presets. - internal LPF on pitch modulation (anti-aliasing) - output normalization (inverse of smoothed instantaneous amplitude) Frequency shifter / ring modulator - coupled with the note pitch and pitch bend for dissonant bending effects - presets for simplified operation LFO and VLFO - LFO: "fast" from 0.1 to 40Hz - VLFO: "slow" from 0.125s to 32s - they generate sine/ramp/inverse ramp/random. - the modulation wheel controls the vibrato. Glide - presets
- separate glide effect for aux oscillator (dissonant transients) MIDI stack - polyphony by stacking (equivalent to round robin) - master/slave automation of sliders through sysex Oscilloscope - helps sound design - automatic sync & gain - one sample per pixel - anti-aliased graphics - Click to freeze it (and save 0.1% CPU) 3 Modulation Sources Even if the c-x-filter synthesizer is not as flexible as a modular synthesizer, you can route modulation sources to four destinations. Modulation sources can be selected to control: c-x-filter Morph c-x-filter Pitch offset c-x-filter Resonance Auxiliary Osc mixing The modulation sources are: ModWheel This is the modulation wheel. Note: the modulation wheel already controls the lfo/vibrato depth. Aftertouch This is the channel aftertouch available on many keyboards. This is a good modulation source for pads "à-la Blade runner". Aux Env (velocity sensitive) This is the auxiliary ADSR envelope, it is velocity sensitive. Aux Env (without velocity sensitivity) The same as above, without velocity sensitivity. Main Env LFO VLFO Sine: a smooth sine-wave Ramp: an ascending sawtooth Inv Ramp: a descending sawtooth Rand: Random steps Same modulation types as the LFO.
Note Rand A random value every time a key is depressed. VLFO + Rand LFO The smooth VLFO sine-wave with a hint of fast randomness, nice for dirty pad sounds. VLFO + LFO The VLFO sine-wave with added "tremolo" from the LFO. Static 0 0.25 0.5 0.75 1 These are not really modulation sources. They are constant values you may use if you do not want to modulate everything... which is a good idea for synthesis of "pseudo-acoustic" sounds. 4 Parameters 4.1 ADSR Envelopes In order to have a limited number of parameters to set, envelopes can be chosen from a set of presets. Nevertheless, you can tweak their global speed with the Time Factor. Main(1) and auxiliary(2) presets: Piano: Organ: Pad: Slow: the classical piano preset, with a slow decay and a fast release. a smooth attack, a constant sustain a smooth release. a soft attack, a constant sustain a soft decay. slower than the Pad.
Very Slow: even slower. Reverso: a reversed envelope, a slow attack and a fast decay with a zero sustain. Breathaway: slow attack, slow decay going back to 0. Harp: a fast decay and a long release. If you want the long release, just hit the keys and don't leave your fingers on the keyboard. Gate: Abrupt attack and release, steady sustain. Bass: An abrupt attack and a short decay & release. Fast Bass: Faster than the preceding. You can use Bass as the main env and Fast Bass as the auxiliary. Long: Just like the piano envelope but longer. Very Long: Even longer. Fast Reverso: a fast reversed envelope. Fast Breathaway. Smooth Bass: a bass envelope with a smooth attack. Oboe: a smooth attack, a long decay, a medium sustain and a smooth release... for soft envelopes. Time Factor(3) 1. From 0.25 to 4: scales the time for both envelopes. 2. From 4 to 7.75: the time scaling depends on velocity at 4 the scaling is 4 at 6 the scaling goes from 4 (low velocity) to 2 (fast velocity) at 7 the scaling goes from 4 to 1 at 7.5 from 4 to 0.5 at 7.75 from 4 to 0.25 4.2 c-x-filter Morph Preset1 (5) and Preset0 (4) Morph Preset1 (5) and Preset0 (4) can be chosen from: Zero: the usual ringing filter with no non-linearities Typical: a typical setting of the cxfilter Classic resonance: a resonating Filter effect Super resonance: almost self oscillating effect Multi-resonance: two resonance oscillations Pulse: produces a series of resonant spikes Square: a symmetrical self-oscillating effect (square like sounds) Super Pulse: asymmetric series of spikes Dirty square: a symmetrical irregular set of spikes Sync lead, Soft sync: sync like waveforms Disto: asymmetric and irregular sync like waveforms Noisy I, Noisy II, Noisy III, Noisy IV: noise modulated effects Modulation sources (6) The morph coefficient can be modulated by a selectable modulation source(6). Pitch offsets (7, 8) The Pitch offsets (7, 8) for the c-x-filters can be chosen between -48 to 48 semitones (+ - 4 octaves) These allow sweep effects.
Pitch offset modulation (9) The Pitch offset can be modulated by a selectable modulation source(9). Resonance modulation(10) The "resonance" of the c-x-filter can be modulated by a selectable modulation source(10). 4.3 Auxiliary oscillator The c X Filter is driven by a main sine oscillator and by an auxiliary oscillator Auxiliary oscillator ratio (11) The frequency ratio of the auxiliary oscillator can be chosen in the list(11). The ratios are sorted by consonance. Consonant sub and over harmonics 2: over oscillator one octave above 1/2, 3/2, 2 + 1/2: sub oscillators and fifth "1/4" ratios, nice for distortion effect 1/4 1-1/4, 1 + 1/4 2-1/4, 2 + 1/4 "1/8" ratios, useful for spooky pads 1/2-1/8, 1/2 + 1/8, 1-1/8, 1 + 1/8, 2-1/8, 2 + 1/8 3 and variants, sharper distortion effects 3, 3-1/2, 3 + 1/2, 3-1/4, 3 + 1/4 Beat cycle (12) The beat cycle(12) is a frequency offset between the main oscillator and the auxiliary oscillator. It can be used to induce sorts of phasing effects. Aux oscillator mix (13) The mixing level of the secondary oscillator can be modulated by one of the usual modulation sources (13). The modulation wheel is a good choice for this one, but you can choose whatever you want. Note: The Auxiliary Oscillator Ratio / Source(11) can also be used to transform the synthesizer into a midi controlled effect by replacing the internal oscillators by the external input. External(11) The external source is processed by the c X filter and the ring modulator. Ring mod External(11) The external source is ring modulated by the main internal oscillator, processed by the c-x-filter, and once more ring modulated by the output ring modulator. 4.4 Ring modulator / Bending mode Ring modulator (14) A ring modulator(14) follows the c-x-filter, it allows dissonant effects and frequency shifting. The presets are:
Normal: No ring modulation, pitch bend +- one octave Square: transposes the spectrum so that even harmonics disappear providing square sounding waveforms. 1/4: transposes to 1/4 of main pitch, nice for subharmonic pads. Square II: a variant of the first Bend Square: when the pitch bend is at full position, the ring modulator induces a "square" frequency shift. Bend Spread: the ring modulator spreads frequencies around. Produces dissonant sounds. Bend Sub Octave: when the pitch bend is at full position, the ring modulator induces a suboctave "square" frequency shift. Bend Sub Fifth: when the pitch bend is at full position, the ring modulator induces a "fifth" frequency shift. Bend Sub Octave2, Bend Sub Fifth2: these are variants to the preceding. Exper 1, Exper 2, Exper 3: experimental and mostly dissonant modes. Low Frequency(16) and Very Low Frequency(15) oscillators VLFO cycle (s) (15) The VLFO is a slow lfo (even if you can set it up to 0.1s ie 10Hz). LFO rate (Hz)(16) The LFO is the "vibrato" oscillator Vibrato depth (cents) (17) This parameter sets the maximum vibrato depth. The vibrato depth is always controlled by the modulation wheel. If you do not want vibrato, simply set this one to 0%. Glide type (18) Glide happens when you play legato. Off: no glide effect. Fast Aux, Med Aux, Slow Aux, Very Slow Aux: the glide only affects the auxiliary oscillator, it induces nice dissonant legato effects. Fast,Med, Slow, Very Slow: the classical glissando effect. Midi stacking(18) MIDI Stack 5, MIDI Stack 4, MIDI Stack 3, MIDI Stack 2, MIDI Stack 1 These are special mode parameters, see "Polyphony by MIDI stacking". 5 Advanced use in effect chains 5.1 Using it as a MIDI controlled effect select "External" or "External and Ring" as "Aux Osc ratio/source (11) to activate the processing of external sources. The cxf plug-in is still MIDI controlled. You can chain a VST-i with the plug-in in the effect chain. The effect is mono (not stereo). 5.2 Chaining As said above, you can chain a cxf synthesizer in synthesizer mode with a cxf synthesizer in effect mode. 5.3 Doubling You can chain cxf synthesizers in synthesizer mode! They will add their outputs together, just like having a pair in parallel.
5.4 Polyphony by MIDI stacking It is possible to stack units in an effect chain to achieve polyphony. Up to 5 units can be stacked. To achieve this, you may use a particular setting. The first c-x-f synthesizer in the chain will be the master, the c-x-f synthesizers after it will be slaves. All slider and preset changes of the master will be transmitted to its slaves through sysex. So, if you want to tweak some parameters, do it on the master synthesizer, not on its slaves. for 2 voice polyphony The parameter "Glide type / MIDI stack"(18) of the master (first in chain) must be "MIDI Stack 2". The parameter "Glide type / MIDI stack"(18) of the slave (second in chain) must be "MIDI Stack 1". for N voice polyphony the parameter "Glide type / MIDI stack"(18) of the master (first in chain) must be "MIDI Stack N". the first slave must be "MIDI stack N-1" The parameter "Glide type / MIDI stack"(18) of the last slave (last in chain) must be "MIDI Stack 1". Note: when recording with Reaper filter out the sysex generated by the synthesizers if you do not want involuntary automation. 6 Files TiaR_CXF_synth_09.jsfx TiaR_KBD_03.jsfx-inc TiaR_ADSR_03.jsfx-inc TiaR_LFO_00.jsfx-inc TiaR_CXF_09.jsfx-inc TiaR_SCP_01.jsfx-inc TiaR_SIN_01.jsfx-inc Main plugin file Midi interface library, includes sysex for sliders and stacking option. ADSR envelope library, includes presets Low Frequency Oscillator library. Based on waveshaped triangle. Complex X filter library. Includes sin/cos oscillator. Oscilloscope library Wave-table based sin/cos oscillator library
7 Schematics