From 4406dd88d1f3f4313149216f3e4cd3d55d2381cb Mon Sep 17 00:00:00 2001
From: Felix Roos <roos@entrecode.de>
Date: Thu, 15 Sep 2022 20:09:07 +0200
Subject: [PATCH] add vowel

---
 packages/webaudio/vowel.mjs    | 37 ++++++++++++++++++++++++++++++++++
 packages/webaudio/webaudio.mjs |  3 +++
 2 files changed, 40 insertions(+)
 create mode 100644 packages/webaudio/vowel.mjs

diff --git a/packages/webaudio/vowel.mjs b/packages/webaudio/vowel.mjs
new file mode 100644
index 00000000..c35b1ebd
--- /dev/null
+++ b/packages/webaudio/vowel.mjs
@@ -0,0 +1,37 @@
+// credits to webdirt: https://github.com/dktr0/WebDirt/blob/41342e81d6ad694a2310d491fef7b7e8b0929efe/js-src/Graph.js#L597
+export var vowelFormant = {
+  a: { freqs: [660, 1120, 2750, 3000, 3350], gains: [1, 0.5012, 0.0708, 0.0631, 0.0126], qs: [80, 90, 120, 130, 140] },
+  e: { freqs: [440, 1800, 2700, 3000, 3300], gains: [1, 0.1995, 0.1259, 0.1, 0.1], qs: [70, 80, 100, 120, 120] },
+  i: { freqs: [270, 1850, 2900, 3350, 3590], gains: [1, 0.0631, 0.0631, 0.0158, 0.0158], qs: [40, 90, 100, 120, 120] },
+  o: { freqs: [430, 820, 2700, 3000, 3300], gains: [1, 0.3162, 0.0501, 0.0794, 0.01995], qs: [40, 80, 100, 120, 120] },
+  u: { freqs: [370, 630, 2750, 3000, 3400], gains: [1, 0.1, 0.0708, 0.0316, 0.01995], qs: [40, 60, 100, 120, 120] },
+};
+
+class VowelNode extends GainNode {
+  constructor(ac, letter) {
+    super(ac);
+    if (!vowelFormant[letter]) {
+      throw new Error('vowel: unknown vowel ' + letter);
+    }
+    const { gains, qs, freqs } = vowelFormant[letter];
+    const makeupGain = ac.createGain();
+    for (let i = 0; i < 5; i++) {
+      const gain = ac.createGain();
+      gain.gain.value = gains[i];
+      const filter = ac.createBiquadFilter();
+      filter.type = 'bandpass';
+      filter.Q.value = qs[i];
+      filter.frequency.value = freqs[i];
+      this.connect(filter);
+      filter.connect(gain);
+      gain.connect(makeupGain);
+    }
+    makeupGain.gain.value = 8; // how much makeup gain to add?
+    this.connect = (target) => makeupGain.connect(target);
+    return this;
+  }
+}
+
+AudioContext.prototype.createVowelFilter = function (letter) {
+  return new VowelNode(this, letter);
+};
diff --git a/packages/webaudio/webaudio.mjs b/packages/webaudio/webaudio.mjs
index 2a6d39d0..18186118 100644
--- a/packages/webaudio/webaudio.mjs
+++ b/packages/webaudio/webaudio.mjs
@@ -9,6 +9,7 @@ import * as strudel from '@strudel.cycles/core';
 import { fromMidi, toMidi } from '@strudel.cycles/core';
 import { loadBuffer } from './sampler.mjs';
 const { Pattern } = strudel;
+import './vowel.mjs';
 
 // export const getAudioContext = () => Tone.getContext().rawContext;
 
@@ -158,6 +159,7 @@ Pattern.prototype.out = function () {
         speed = 1, // sample playback speed
         begin = 0,
         end = 1,
+        vowel,
       } = hap.value;
       const { velocity = 1 } = hap.context;
       gain *= velocity; // legacy fix for velocity
@@ -258,6 +260,7 @@ Pattern.prototype.out = function () {
       cutoff !== undefined && chain.push(getFilter('lowpass', cutoff, resonance));
       hcutoff !== undefined && chain.push(getFilter('highpass', hcutoff, hresonance));
       bandf !== undefined && chain.push(getFilter('bandpass', bandf, bandq));
+      vowel !== undefined && chain.push(ac.createVowelFilter(vowel));
       // TODO vowel
       // TODO delay / delaytime / delayfeedback
       // panning