In this episode of Frap Talks we’ll talk about trigs, and we’ll see how to use them in our Frap System.

Transcript

Hello, and welcome to Frap Talks, where we discuss anything related to modular synthesis with frap tools instruments.

Today we’ll start with a question. What do music, bakery, and connecting flights have in common?

It’s timing. Music, bakery, and flights are all about events happening at the right moment.

In modular synthesis, what defines the timing of our musical elements are trigs and gates, which are often called timing pulses.

Timing pulses are a specific kind of control voltages. They are called timing because their primary role is to tell the synthesizer when certain events must happen, and they are called pulses because they have only two voltage values, high or low. The transition between them is very steep, almost immediate, like an impulse.

We use timing pulses to generate musical events, such as notes, melodies, or rhythmic elements.

There are two kinds of timing pulses: trigs and gates. The difference between them is that gates can have a duration, while trigs are short voltage bursts that usually last just a few milliseconds.

Trigs define when a musical event should happen, and gates can define when a musical event should happen, but also for how long.

We can use trigs when the musical event we seek need doesn’t need different durations throughout our composition, such as percussive elements. However, if we need to define, for example, the duration of a note, we need a gate.

We have said that timing pulses have only two values, low or high. In the Eurorack world, a gate signal is low when its value is 0Volts, and it is high when it is somewhere around or above 5 volts.

The High or Low voltages may differ from one manufacturer to another, but all the gates have one thing in common: their values pretty much remain steady throughout each state. In other words, they output two voltages that are not continuous.

This is the reason why they are called Gates: because even in real life, a gate that is just half-open does not serve any clear purpose: we need it to be either close or open.
Open and closed are, in fact, some terms that stand for high or low voltages, respectively: usually, a gate is open while it is used to let something happen and closed when it does not.

The transition from gate low to gate high is often used to mark the beginning of a musical event; the time a gate stays high determines its duration; the transition from high back to low marks its end.

On the other hand, the trig is just a rising transition immediately followed by a falling one.

We will cover gates in other videos of this series: for now, let’s dig into trigs!

In this system here, the main trig generator is SAPÈL. It is a random voltage generator, so it does many other things, but today we’ll focus on this one.

SAPÈL has two clocks inside: a clock is basically a circuit that outputs a regular stream of equally-spaced trigs. If we patch a clock output straight into the CGM channel, we can hear its regular beat.

It would be daring to call this music, but it’s a regular beat, and where there’s rhythm, there can be music. However, in general, trigs and timing pulses aren’t meant to be used as a sound source but rather to control the articulation of other musical events (or the whole composition, in the case of the clock).

In this first patch, we are using FALISTRI to control the amplitude of our sound source (the BRENSO oscillator).

We have set its green generator to Hold mode to demonstrate its function. If we push the button, we generate a musical event whose duration depends on how long we keep our fingers pressed. Such a musical event can also have slow transitions at the beginning and at the end, whose time depends on the knob settings. We can replace this behavior by patching SAPÈL’s clock output to FALISTRI’s Trig/Gate input.

However, in this way, since SAPÈL outputs trigs, which do not have any length information, our musical events will be all of the same, short lengths.

In the second patch, SAPÈL’s clock output controls the tempo of our USTA sequencer. CV A controls the pitch of the BRENSO oscillator, and gate A trigs an envelope that controls the amplitude, just like in the previous patch. The core principle is pretty much the same so that if we increase the speed of SAPÈL’s clock output, we will increase the speed of the whole sequence.

The BRENSO oscillator has a wavefolding circuit that adds harmonic distortion to the sound. However, we can use it as a colored VCA to add dynamics to our patches.

We can patch a timing pulse such as SAPÈL’s clock output to BRENSO’s ping input. The ping circuit internally generates an envelope that opens the wavefolder and closes it with an organic decay. We can rotate the ping decay knob and change the duration of this envelope.

We can also patch SAPÈL’s random clock output, set to work in Less Than mode, to the trig input of one of FALISTRI’s envelopes. We then patch the envelope to the wavefolder CV input and adjust its modulation amount. The result is similar yet distinct and provides nice harmonic accents here and there.

In the third patch, SAPÈL’s clock output trigs an envelope that controls the amplitude of our sound source. The melody, however, is triggered by the random clock, which moves the playhead of the USTA sequencer forward every now and then. The result is a random melody with a steady pulse.

In the fourth patch, we are using FUMANA to filter some pink noise. First, we need to turn down all the filters levels; then, we’ll perform some spectral transferring.

If we patch any sound source to the modulation input, FUMANA will transfer its harmonic content to the white noise patched to the main input. In this case, we’re using a sawtooth wave from the BRENSO oscillator.

However, things become interesting if we patch a Sapèl’s trigs straight to FUMANA’s MOD input. The result is a percussive and organic tone with a very natural decay.

We can add some variation to the patch by using SAPÈL’s random clock output. At the same time, we can use the main clock output to trig an envelope on FALISTRI that we will patch to the parametric scanning control.

The parametric scanning section acts as a sort of global modulation of the filter levels. We are not performing spectral transferring anymore with this envelope: instead, we are just applying a more standard CV modulation.