inscript -> notes -> synthesis -> slope generator concepts

*under construction*

an idealized slope generator
an idealized "black box" slope generator

The voltage-controllable slope generator (or Universal Slope Generator as coined by Serge Tcherepnin) is an extremely versatile device for generating and modifying signals at a variety of frequencies.

Below are some examples of patches that I have gathered from across the internet. I do not claim any owenership of these concepts and have done my best to properly cite the most direct source or author. Please contact me if you would like anything to be credited differently or taken down.

VC Transient Envelope Generator1

A pulse at the trigger input will start the envelope, or a gate input will sustain the level and the envelope will fall when the gate goes low. Rise and fall are independently and jointly voltage controllable, with variable linear and exponential wave shapes. VC Portamento

Voltage is slewed according to the rise and fall times.

VC LFO1

When the cycle switch is thrown, the trigger input is connected internally to the end trigger output, creating a VC clock with variable waveform and independent rise and fall times.

VC Oscillator

While not as wide ranged, or accurate as a dedicated oscillator module, the VCS is still an excellent audio source. The Exp CV input is scaled approximately to the 1v/oct standard. The Output wave can be swept from triangle to saw with linear and non-linear waveforms. End Out also produces a pulse waveform.

VC Non-Linear Audio Processor (Low-Pass Gate)1

If an audio rate signal is slewed, the module responds like a VCF, and a rough VCA. The signal is low-pass filtered down to silence, similar to a low-pass gate.

Envelope Follower1

Positive and negative peak detection envelope follower.

VC Pulse Delay1

Trigger input starts the envelope and a trigger will be produced again at the ”End Out” when the envelope completes its cycle.

Sub-Harmonic Generator1

If a series of triggers are applied to the VCS faster than the total rise and fall times, the module will divide the incoming signal by a whole number. In the audio range the output will be the sub-harmonic series.

Triangle VCO2

8 note sequence from an analog sequencer at the Exp CV input. cycle = on rise = 12 o'clock fall = 12 o'clock both slopes linear

Skimmed Sawtooth VCO2

8 note sequence from an analog sequencer at the exp cv input. cycle = on rise = 12 o'clock fall = 12 o'clock vc rise = fully ccw exponential vc fall = fully cw exponential

Narrow Pulse VCO2

8 note sequence from an analog sequencer at the exp cv input. cycle = on rise = 12 o'clock fall = 12 o'clock vc rise = linear vc fall = fully cw exponential

Low Pass VCF + VCA Response2

Analog sequence is now sent to a VCO. Sawtooth output goes to the VCS Input. A slow triangle wave from an LFO goes to the VC Both input. cycle = off rise = fully ccw fall = fully ccw both slopes linear

High Pass VCF + VCA Response2

Same patch as above, but this time the slow triangle LFO is patched to VC Fall only. cycle = off rise = fully ccw fall = fully ccw vc rise = linear vc fall = 9 o'clock exponential

Sync + Low Pass + VCA2

Analog sequence is sent to two slightly detuned VCOs. As above the sawtooth of VCO1 goes to the VCS Input. The squarewave from VCO2 goes to the VCS Trigger Input. The slow triangle LFO goes to the VC Both input. cycle = off rise = fully ccw fall = fully ccw vc rise = 1 o'clock linear vc fall = 1 o'clock linear

VC Waveshaper2

VCO Sawtooth to VCS Input. A triangle wave from the same VCO is patched to the VC Both input. cycle = off rise = fully ccw fall = fully ccw both slopes exponential, starting fully cw First the VC Fall knob is turned from fully cw to fully ccw. Then the VC Rise knob is turned from fully cw to fully ccw.

Animated Wave2

2 VCOs are slightly detuned, the sine from VCO1 is fed to the VCS Input while the sine from the second VCO is fed to the VC Both input. cycle = off rise = fully ccw fall = fully ccw vc rise = fully cw exponential vc fall = fully ccw exponential

VC Slew Limiter2

Standard slew with equal rise and fall times: Audio source is a VCO pulse wave. Pulsewidth is modulated by the sinewave of another VCO. The Analog sequencer CV goes into the VCS Input. VCS Output is fed into the 1v/oct CV input of both VCOs. Slew time is modulated by a slowly increasing positive control voltage at the VC Both input. cycle = off rise = 2 o'clock fall = 2 o'clock vc rise = fully cw linear vc fall = fully cw linear

Same patch as above, but the VCS is in Cycle mode. The voltage at the VC Both input goes from -5 volts in the beginning to +5 volts at the end.

VC LFO2

VCS Output modulates the cutoff frequency of Low Pass Filter. cycle = on rise = 3 o'clock fall = 3 o'clock both slopes linear

VC Envelope Generator2

Audio source is a filtered VCO pulse wave. The pulsewidth is modulated by the sinewave of another VCO. Filter cutoff is modulated by the VCS Output. The VCS is triggered with each note. A second sequencer row goes into the VC Fall input for increasing the decay time on three of the eight notes in the sequence. cycle = off rise = fully ccw fall = 2 o'clock vc rise = fully cw exponential vc fall = 1 o'clock exponential

VC Pulse Delay2

Audio source is a filtered VCO pulse wave. The pulsewidth is modulated by the sinewave of another VCO. The filter is a multimode filter in lowpass mode. Two adsr envelopes are used for cutoff modulation. Every note triggers the first envelope and also the VCS. The second envelope is triggered by the end out of the VCS. In the first half of the recording the filter is modulated by the first envelope only. In the second half you hear a modulation from both envelopes. cycle = off rise = 10 o'clock fall = 2 o'clock both slopes linear

VC Envelope Follower2

The audio source is an analog drum machine, coming into the system through an external input module. From there the audio signal is fed into the VCS Input and a lowpass filter. The cutoff of the filter is modulated by the VCS Output. A variable control voltage at the VC Both input is used to modulate the slew time of the envelope follower. The voltage is slowly increasing from -10 volts in the beginning to +10 volts at the end. cycle = off rise = 9 o'clock fall = 12 o'clock vc rise = half past 1 linear vc fall = half past 1 linear

Slope Generator as Subharmonic/Undertone Generator from Nav of Nav's Modular Lab3

If a series of triggers are applied to the VCS faster than the total rise and fall times, the module will divide the incoming signal by a whole number. In the audio range the output will be the sub-harmonic series.

The VCS has the benefit of an AC-coupled output, but I feel Maths offers finer control over the settings. As this patch relies on the rise time, Math's EOR pulse can be used to provide an even beefier sub signal.

The technique simply involves patching a mult of your principal oscillator to Maths' trigger input and mixing either the envelope or EOR with the main VCO in a filter etc. Set the response to linear, fall to fully CCW and then gradually increase the rise time. Additionally altering the fall time will give you more control over the timing and hence sub-divisions.

AR EG4

Patch a Gate or Trigger signal into the "TRIG IN" jack. A attack-release (AR) voltage envelope is generated at the "OUTPUT" jack with its attack and release times controlled by the "RISE" and "FALL" pots respectively.

ASR EG4

An attack-sustain-release envelope is implemented by routing a Gate signal into the "INPUT" jack. The resultant EG output will sustain as long as a Gate is present. Again, the attack and release times are controlled by the "RISE" and "FALL" pots respectively.

HINT: The above envelopes are linear envelopes. For an exponential response, stack a banana cable on the "OUTPUT" and patch it to the "VC IN" jack and adjust the "VC" pot positively to taste. The "RISE/BOTH/FALL" switch selects which part(s) of the envelope become exponential.

HINT: Complex envelope shapes can be created by mixing the outputs of more than one Slope Generator together into a single signal with a voltage mixer like an ACPR, MPRO or a PRC. For instance, if driven by the same gate, you could have one half a DSG doing the "AD" portion and the other half the "SR" portions of an ADSR envelope with unique control possibilities.

One interesting thing to note is that when an envelope finishes its cycle, the "GATE OUT" jack generates a new gate - which leads into the next use of a DSG - LFOs.

LFOs4

Low Frequency Oscillators are relatively easy to make. Lets start by patching the "GATE OUT" jack to the "TRIG IN" jack just below it. The DSG will start to oscillate all by itself with its frequency determined by the "RISE" and "FALL" knobs. Watch the LED for a visual reference of overall frequency as well as the rise and fall times. To obtain a square wave, stack another banana cord on the "GATE" jack. To obtain a triangle wave, patch a cord into the "OUTPUT" jack and you'll have a triangle or saw wave. One nice feature of this waveform is you can control its shape by adjusting the "RISE" and "FALL" knobs. A short rise and slower fall gives a regular Saw waveform, a slow rise and quick fall gives a Reverse Saw and equal rise and fall times result in a Triangle. You can modulate the /shape/ of this waveform by patching a CV into the "VC IN" jack and setting the modulation target with the "RISE/BOTH/FALL" switch.

HINT: Complex composite LFO waveforms can be created by mixing the outputs of more than one Slope Generator together into a single signal with a voltage mixer like an ACPR, MPRO or a PRC.

HINT: To "soften up" a triangle or square waveform (or even a more complex composite LFO waveform), run it through an available 1/2 DSG patch-programmed as a Slew Generator (see "Directional CV Glide" below).

Audio Oscillator4

Let's speed things up a bit, shall we? Everything we learned about using the DSG to make LFOs is applicable here for audio oscillators as well - all we need to do to the above patch is to route a CV of choice into the "1V/OCT" input jack to drive the pitch of the oscillator. The TKB or various Sequencers are a great source of preset CVs.

The DSG doesn't track so hot in the higher registers (and won't track at all above a certain pitch) but is an excellent source of bass and mid-range tones with lots of character.

HINT: To "warm up" your oscillator, try running it through the top section of a Wave Multipliers function block with its switch set to "HI", you'll get a soft-clipped sound similar to a tube amp.

HINT: When mixing audio oscillators, sometimes it helps to invert one or more of the signals to help avoid "cancellation" issues, especially if you have a lot of feedback going on - unless that's the effect you're going for.

Trigger/Gate Delay4

Here's another deceptively simple patch that makes a great building block for more complex patches. Patch your Trigger or Gate signal into the "TRIG IN" jack and take your delayed signal from the "GATE OUT" jack. The amount of delay is set by the sum of the "RISE" and "FALL" knobs. You may need to invert the output depending on whether you need a rising edge or falling edge for your application.

Subharmonic Generator4

This patch works in a similar fashion to the Gate Delay patch above. What we're doing is setting the DSG to be re-triggered by the incoming signal like before but this time the source signal will be an audio signal and the DSG's output will be an audio rate square wave that will be a subharmonic of the original signal. Patch your signal into the "TRIG IN" jack and take the output from the "GATE OUT" jack. This patch will take some tweaking to "tune" to taste.

HINT: Square up the audio signal with a comparator first (or simply use a square/pulse wave oscillator) so the DSG's "TRIG IN" receives reliable triggers.

Envelope Follower4

Patch your audio signal into the black "INPUT" jack and set the "RISE" knob very fast (clockwise). Begin with the "FALL" knob set very fast but slowly bring it down (counter-clockwise" until the signal at the "OUTPUT" jack is following the peaks and valleys of the audio signal's volume envelope. This is another patch you will have to "tune" by ear - have fun!

Directional CV Glide4

Patch your CV into the "INPUT" jack and your slewed version will be available at the "OUTPUT" jack. The "RISE" and "FALL" knobs will set the slewing up or down of the original CV respectively. An obvious implementation of this is to patch a CV destined to control an oscillator's pitch through here to create "glide" or portamento - with the added trick that your portamento doesn't have to be bi-polar, you can have glide only on upward pitch changes, only on downward pitch changes or even have /different amounts of glide/ on up and down pitch changes. Of course you're not limited to "pitch CVs" alone but can process /any/ CVs this way.

HINT: The above patch has a linear response. An exponential response can be created by stacking a patch cable from the "OUTPUT" jack to the "RISE/BOTH/FALL" VC in jack and adjusting the curve to taste with the "VC" knob.

HINT: Patch an audio signal in place of the CV and set both "RISE" and "FALL" knobs relatively fast and the patch becomes a lo-fi Low Pass Filter. Patch a CV into the "RISE/BOTH/FALL" jack to make the filter voltage-controllable.

Lopsided Recursive Waveform Generator4 Patch a couple of Triangle/Saw LFOs using both halves of a DSG then patch the waveforms of each into the "RISE/BOTH/FALL" CV input jacks of the other. Adjust to taste. Tap the waveform out by stacking a patch cord on one of the outputs and route it somewhere that needs a lopsided, recursive waveform.

references|further:

1) Seth Nemec's Voltage Controlled Slope page via Bananalogue Site⭧

2) Ingo Zobel's Slope Patches originally submitted to the Bananalogue Site⭧

3) Nav's Modular Lab⭧

4) James D. Maier's Notes on patching the Serge DUSG⭧

Serge DUSG Patching Techniques via Muffwiggler Forum⭧

An interesting article by Kassutronics⭧ on a DIY USG-inspired slope generator https://kassu2000.blogspot.com/2016/04/slope-generator.html