12. Operators, for Animating Musical Sequences

Music is normally conceived in a rough, fuzzy way and then programmed into the computer as an expression of stark certainty. If only some of the composer's thought process could be entrusted to the computer, so that changing circumstances might yield different, symmetric results. And this is why Bitwig has Operators.

Operators change when or how notes and audio events are triggered. In other words, Operators allow you to take sequenced events and animate them with randomness, cycle-aware logic, performance controls, and other interrelationships that expand what a clip is capable of.

Let's spend a moment with this pile of various and sundry ideas.

Randomness, weighting any event to be more or less likely each time the play head arrives.
Cycle-aware logic, considering how many times a clip has looped. So events can be triggered only on (or after) a clip's initial loop, or an event can think in a number of cycles (say, six loops per cycle) and then trigger on the first, second, and fourth loops each time.
Performance controls, mapping events to play (or not) when the mappable Fill button is on.
Interrelationships between events, so events play only when the previous event did (or didn't).
Even the simplest idea — turning a single event into countless, ramping retriggers — multiplies your sound design possibilities while keeping the mayhem manageable.

These are strong ideas individually (and they do make appearances all thru Bitwig Studio). But they are together within Operators, which can shift the compositional process a bit, allowing you to program conditional relationships between events and much more.

We'll start by examining each of the four Operator modes. Then we'll look at a few functions that relate to Operators in one way or another. And after you've played with the Operators one at a time, do try them together (maybe Chance on one event, followed by without Previous on the next). Because while each mode has its charms, simple combinations can yield exquisitely musical results.

Operator Modes

When note or audio events are selected, an Operators section is visible in the Inspector Panel. Each line represents one of the four Operator modes, with most parameters available right there.

For any new event — whether by drawing notes, or splitting an audio clip, or recording either notes or audio, etc. — all Operators are set to neutral states, which have no effect other than to play back a normal event each and every time the playhead passes it. These default values will be noted below.

But note that mode icons also double as toggles. So if you try something new with Occurrence settings, you can always click the if button to temporarily bypass just the Occurrence behaviors for the selected events. By default, all of these modes are enabled, which means that trying out any Operator is as simple as selecting some notes or audio events, and setting a value in the Inspector Panel.

As each mode is unique, let's spend a moment with each of them.

Chance

Chance sets the likelihood that any event will occur, adding a mercurial element to your events.

Chance only has a single parameter, which represents the probability that this event will play. So if an event's Chance value is set to 50 % (half of the time) and the clip plays four times, the event is most likely to play two of the times and to not play the other two times.

Chance is visualized on each event like the face of a die (dice). The number of dots or spots shown represents the current setting:

5 dots - 80 % to almost 100 %
4 dots - 60 % to almost 80 %
3 dots - 40 % to almost 60 %
2 dots - 20 % to almost 40 %
1 dot - 0 % to almost 20 %

For example, the following series of notes goes from high to low probability, and then back up again.

And when working with notes, the Chance expressions have their own editor, appearing right after the velocity expressions (see Chance Expressions).

All this talk of "most likely" and what is "probable" reminds us that Chance is random. So other than its default value (a neutral 100 %, meaning always) or a setting of 0 % (read: never), every other value is perfectly unpredictable for any single moment.

As the one randomized Operator, Chance is determined by the clip's Seed parameter (see Seed Section). This makes its behavior identical to expression Spread (see Expression Spread).

And if only using the Chance Operator on an event, you will see at the start of each clip cycle whether that event will play or not. For notes, a full stroke around the note shows that it will play this time. For audio events, a normal, bright color stripe in the audio event header indicates it will trigger.

	Note
	Not all Operators produce playback visualization. So when multiple Operators are in use, you may see the visualization for a positive Chance outcome, but the event might not trigger for other reasons.

Repeats

Repeats causes retriggers within the original event, letting any single event create (and control) myriad more.

Repeats has at least two parameters.

Repeat Rate determines when the retriggers will happen. It defaults to Off (no effect; the same as typing in 1 or 0 [zero]), and this parameter actually has two modes.
When dragging upward, you scroll thru positive numbers (2, 3, up to 128). This sets the number of pieces that the event is divided into. This also means that changing the length of the event will change the placement of its repeats.
If you drag downward, you go thru fractions (1/2, 1/3, up to 1/128). This sets the rate at which repeats will occur in beat time, which is not affected by the length of the event. And while any value is available, some standard musical intervals are available in a pop-up menu by right-clicking on the Repeat Rate parameter itself.
Repeat Curve is represented by the horizontal slider beside Repeat Rate. The default value is centered (0 %), which keeps all repeats in their original position. Negative values (to the left of center) set the repeats to be closer together at the start of the event, and positive values (to the right of center) bunch the repeats closer together toward the event's end.

These two parameters determine the placement and timing of the repeats. Each event retrigger acts like a restart of the note or audio, with a visualization that clearly shows the placement and effect. For audio events, the waveform is shown restarting to match the playback behavior.

For notes, Repeats has two additional parameters related to velocity.

Repeat Velocity End sets the target velocity for the end of the repeats. Since velocity is only used at the beginning of each note, this level may never be reached, but the curve will be maintained if the rate or timing of repeats is changed. The parameter range is a bipolar percentage, mapping the end point relatively across the full velocity range.
So let's assume a note with a velocity of 40 %. A Repeat Velocity End setting of 0 % would represent no change, starting every repeat with the original note velocity. A Repeat Velocity End value of 50 % would initially trigger at velocity 40 % with the successive repeats ramping up to a velocity of 70 %. And a Repeat Velocity End value of -75 % would initially trigger at velocity 40 % with the successive repeats tapering down toward a velocity of 10 %.
Repeat Velocity End is found at the right end of the Repeats line in the Inspector Panel, beside the vertical velocity pin icon (when notes are selected). It is also visualized in the velocity expressions lane as a draggable handle at the end of the note.
Repeat Velocity Curve is available inside the velocity expression lane. By holding ALT and dragging the velocity end handle up or down, the curve of any repeated event can be bent to move toward the target velocity sooner or later.

One final note. Any note or audio event using the Repeats Operator is still a single event — at least until you choose to Slice At Repeats (see Slice At Repeats). And as a single event, expressions can be draw across the length of each event, including across repeats.

Occurrence

Occurrence sets conditions for each event. The choice of Condition is presented in a single menu.

For any event using Occurrence, the icon for the selected Condition is shown on the event. And as we go thru each Condition, keep in mind that they are each self-contained with no additional parameters.

Always - The event will play every time. This is the default, neutral state.
on First - Plays on the first pass (including retriggers) of the clip
never First - Plays every time except on the first pass (including retriggers) of the clip
with Previous - Plays if the immediately previous event did
without Previous - Plays if the immediately previous event didn't
with Prev Key [note events only] - Plays if the immediately previous note on this key did
without Prev Key [note events only] - Plays if the immediately previous note on this key didn't
with Prev Chan. [note events only] - Plays if the immediately previous note on this channel did
without Prev Chan. [note events only] - Plays if the immediately previous note on this channel didn't
Fill on - Plays when Fill mode is on, in the global transport (see Transport Section)
Fill off - Plays when Fill mode is off, in the global transport (see Transport Section)

So thinking of the list from the start of this chapter, Occurrence includes cycle-aware options (the two First modes), interrelationships (all modes using the Previous idea), and performance controls (Fill on and Fill off).

	Note
	Of the Occurrence modes, only the two First modes provide playback visualization.

Recurrence

Recurrence gives each event its own looping timeline.

As shown above in the Inspector Panel, there are two parameters along with one visualization element that make this work.

Recurrence Length sets the number of loops per cycle for this event. This can be set between 1 (the default, neutral value, shown as Off) and 8.
Following the length value is a matching number of toggle boxes. Each Recurrence Step is clickable to toggle whether the event will trigger on that particular loop of the cycle.
You'll also notice an underline beneath one of the step toggles. This little indicator tells you which loop of the cycle is currently playing back.

This pattern is also shown on the right edge of events themselves, with a series of shaded (on) and empty (off) rectangles.

And finally, Recurrence does provide playback visualization on each event when a loop cycle is started.

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