Merge pull request 'Signal flow documentation' (#1504) from glossing/strudel:glossing/signal-flow-documentation into main

Reviewed-on: https://codeberg.org/uzu/strudel/pulls/1504
Reviewed-by: Switch Angel AKA Jade Rose <daslyfe@noreply.codeberg.org>

website/src/pages/learn/effects.mdx

@@ -11,6 +11,129 @@ import { JsDoc } from '../../docs/JsDoc';
 Whether you're using a synth or a sample, you can apply any of the following built-in audio effects.
 As you might suspect, the effects can be chained together, and they accept a pattern string as their argument.
 
+# Signal chain
+
+<img src="/img/strudel-signal-flow.png"></img>
+
+The signal chain in Strudel is as follows:
+
+- An sound-generating event is triggered by a pattern
+  - This has a start time and a duration, which is usually
+    controlled by the note length and ADSR parameters
+  - If we exceed the max polyphony, old sounds begin to die off
+  - Muted sounds (one whose `s` value is `-`, `~`, or `_`) are skipped
+- A sound is produced (through, say, a sample or an oscillator)
+  - This is where detune-based effects (like `detune`, `penv`, etc. occur)
+- The following will occur _in order_ and only if they've been called in the pattern. Note that all of these are
+  single use effects, meaning that multiple occurrences of them in a pattern will simply override the values
+  (e.g. you can't do `s("bd").lpf(100).distort(2).lpf(800)` to lowpass, distort, and then lowpass
+  again)
+  - Phase vocoder (`stretch`)
+  - Gain is applied (`gain`)
+    - This is where the main (volume) ADSR happens
+  - A lowpass filter (`lpf`)
+  - A highpass filter (`hpf`)
+  - A bandpass filter (`bandpass`)
+  - A vowel filter (`vowel`)
+  - Sample rate reduction (`coarse`)
+  - Bit crushing (`crush`)
+  - Waveshape distortion (`shape`)
+  - Normal distortion (`distort`)
+  - Tremolo (`tremolo`)
+  - Compressor (`compressor`)
+  - Panning (`pan`)
+  - Phaser (`phaser`)
+  - Postgain (`post`)
+- The sound is then split into multiple destinations
+  - Dry output (amount controlled by `dry` parameter)
+  - The sends
+    - Analyzers
+      - These are used for tooling like `scope` and `spectrum` and their setup usually happens behind the scenes
+    - Delay (amount controlled by `delay` parameter)
+    - Reverb (amount controlled by `room` parameter)
+- The dry output, delay, and reverb are joined into what is called the "orbit" of the pattern (see more in the section below)
+  - The `duck` effect affects the volume of all signals in the orbit
+  - The orbit is then sent to the mixer
+
+## Orbits
+
+Orbits are the way in which outputs are handled in Strudel. They also prescribe which delay and reverb to associate with the dry signal.
+By default, all orbits are mixed down to channels `1` and `2` in stereo, however with the "Multi Channel Orbits" setting
+(under Settings at the right) you can use them as individual 2 channel stereo outs (orbit `i` will be mapped to
+to channels `2i` and `2i + 1`). You can then use routers like Blackhole 16 to retrieve and record all of the channels in a DAW for later processing.
+
+The default orbit is `1` and it is set with `orbit`. You may send a sound to multiple orbits via mininotation
+
+<MiniRepl client:visible tune={`s("white").orbit("2,3,4").gain(0.2)`} />
+
+but please be careful as this will create three copies of the sound behind the scenes, meaning that if they are mixed
+down to a single output, they will triple the volume. We've reduced the gain here to save your ears.
+
+⚠️ There is only one delay and reverb per orbit, so please be aware that if you attempt to change the parameters on two
+patterns pointing to the same orbit, it can lead to unpredictable results. Compare, for example, this pretty pluck
+with a large reverb:
+
+<MiniRepl
+  client:visible
+  tune={`
+$: s("triangle*4").decay(0.5).n(irand(12)).scale('C minor')
+  .room(1).roomsize(10)`}
+/>
+
+versus the same pluck with a muted kick drum coming in and overwriting the `roomsize` value:
+
+<MiniRepl
+  client:visible
+  tune={`
+$: s("triangle*4").decay(0.5).n(irand(12)).scale('C minor')
+  .room(1).roomsize(10)
+
+$: s("bd\*4").room(0.01).roomsize(0.01).postgain(0)`}
+/>
+
+This is due to them sharing the same orbit: the default of `1`. It can be corrected simply by updating the orbits to be
+distinct:
+
+<MiniRepl
+  client:visible
+  tune={`
+$: s("triangle*4").decay(0.5).n(irand(12)).scale('C minor')
+  .room(1).roomsize(10).orbit(2)
+
+$: s("bd\*4").room(0.01).roomsize(0.01).postgain(0)`}
+/>
+
+## Continuous changes
+
+As all of the above is triggered by a _sound occurring_, it is often the case that parameters may not be
+modified continuously in time. For example,
+
+<MiniRepl
+  client:visible
+  tune={`
+s("supersaw").lpf(tri.range(100, 5000).slow(2))`}
+/>
+
+Will not produce a continually LFO'd low-pass filter due to the `tri` only being sampled every time the note hits
+(in this case the default of once per cycle). You can fake it by introducing more sound-generating events, e.g.:
+
+<MiniRepl
+  client:visible
+  tune={`
+s("supersaw").seg(16).lpf(tri.range(100, 5000).slow(2))`}
+/>
+
+Some parameters _do_ induce continuous variations in time, though:
+
+- The ADSR curve (governed by `attack`, `sustain`, `decay`, `release`)
+- The pitch envelope curve (governed by `penv` and its associated ADSR)
+- The FM curve (`fmenv`)
+- The filter envelopes (`lpenv`, `hpenv`, `bpenv`)
+- Tremolo (`tremolo`)
+- Phaser (`phaser`)
+- Vibrato (`vib`)
+- Ducking (`duckorbit`)
+
 # Filters
 
 Filters are an essential building block of [subtractive synthesis](https://en.wikipedia.org/wiki/Subtractive_synthesis).