create/update 'fadein sample code.md' file

strudel/fadein sample code.md

@@ -0,0 +1,74 @@
+```javascript
+// @title fading @by ACorp
+// @license 0BSD
+
+setCpm(60 / 2)
+
+const latch = (f) => {
+  let start = undefined;
+  return signal((t) => {
+    start = start ?? t;
+    return f(t - start);
+  });
+}
+
+const ramp = (cycles) => latch((t) => Math.min(t / cycles, 1));
+const iramp = (cycles) => latch((t) => Math.max(1 - t / cycles, 0));
+register('fadein', function(cycles, gainstart, gainstop, pat) {
+  return pat.gain(ramp(cycles).range(gainstart, gainstop));
+})
+
+const shush = [Math.pow(2,32)-1, silence];
+
+const chords = chord("<CM9 Am7 Dm9 Gm7>").voicing()
+const nchords = p => n(p).chord("<CM9 Am7 Dm9 Gm7>").voicing()
+const i1 = chords.s("supersaw").lpf(800)
+  .ph(3).phd(1).phc(4000).room(2)
+
+const parts = [20, 32, 8, 80]
+const sparts = (start, stop) => parts
+  .slice(start, stop + 1)
+  .reduce((sum, val) => sum + val, 0);
+
+
+i1$: arrange(
+  [sparts(0,1), i1.fadein(parts[0], 0.2,1)],
+  [parts[2], silence],
+  [parts[3], i1],
+  shush
+)
+
+const i2 = nchords("[3,4] - - -").s("square,pulse")
+  .decay(0.2).release(0.4)
+  .lpf(1600).gain(0.6)
+
+i2$: arrange(
+  [parts[0],silence],
+  [sparts(1,3), i2],
+  shush
+)
+
+const i3 = nchords("1,2")
+  .struct("1 0 1 1 0 1 1 0")
+  .s("tri,pulse")
+  .ply("2 0 1 2 1 2 2 0")
+
+i3$: arrange(
+  [parts[0],silence],
+  [sparts(1,3), i3.fadein(parts[1], 0.2,1.2)],
+  shush
+)
+
+const i4 = nchords(irand(4).seg(8).add(2))
+  .mask("1 <[0 1] 1> 1 <0 [1 0] [1 0 1] 1> 1")
+  .s("gm_piano").n("0,1")
+  .lpf(2000).rarely(x=>x.ply("2"))
+
+i4$: arrange(
+  [sparts(0,2), silence],
+  [parts[3], i4],
+  shush
+)
+
+all(x=>x.postgain(0.8))
+```