diff --git a/packages/core/pattern.mjs b/packages/core/pattern.mjs
index 15425397..c5f7a6be 100644
--- a/packages/core/pattern.mjs
+++ b/packages/core/pattern.mjs
@@ -1361,6 +1361,49 @@ export class Pattern {
   }
 }
 
+//////////////////////////////////////////////////////////////////////
+// functions relating to chords/patterns of lists
+
+// returns Array<Hap[]> where each list of haps satisfies eq
+function groupHapsBy(eq, haps) {
+  let groups = [];
+  haps.forEach((hap) => {
+    const match = groups.findIndex(([other]) => eq(hap, other));
+    if (match === -1) {
+      groups.push([hap]);
+    } else {
+      groups[match].push(hap);
+    }
+  });
+  return groups;
+}
+
+// congruent haps = haps with equal spans
+const congruent = (a, b) => a.spanEquals(b);
+// Pattern<Hap<T>> -> Pattern<Hap<T[]>>
+// returned pattern contains arrays of congruent haps
+Pattern.prototype.collect = function () {
+  return this.withHaps((haps) =>
+    groupHapsBy(congruent, haps).map((_haps) => new Hap(_haps[0].whole, _haps[0].part, _haps, {})),
+  );
+};
+
+// applies func to each array of congruent haps
+Pattern.prototype.arpWith = function (func) {
+  return this.collect()
+    .fmap((v) => reify(func(v)))
+    .squeezeJoin()
+    .withHap((h) => new Hap(h.whole, h.part, h.value.value, h.combineContext(h.value)));
+};
+
+// applies pattern of indices to each array of congruent haps
+Pattern.prototype.arp = function (pat) {
+  return this.arpWith((haps) => pat.fmap((i) => haps[i % haps.length]));
+};
+
+//////////////////////////////////////////////////////////////////////
+// compose matrix functions
+
 // TODO - adopt value.mjs fully..
 function _composeOp(a, b, func) {
   function _nonFunctionObject(x) {
diff --git a/repl/src/test/__snapshots__/tunes.test.mjs.snap b/repl/src/test/__snapshots__/tunes.test.mjs.snap
index 1de13d99..4097dc7a 100644
--- a/repl/src/test/__snapshots__/tunes.test.mjs.snap
+++ b/repl/src/test/__snapshots__/tunes.test.mjs.snap
@@ -39,6 +39,35 @@ exports[`renders tunes > tune: amensister 1`] = `
 ]
 `;
 
+exports[`renders tunes > tune: arpoon 1`] = `
+[
+  "0/1 -> 2/3: {\\"note\\":55.000528662214684,\\"cutoff\\":509.2515887569149,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5249999999999999,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "0/1 -> 2/3: {\\"note\\":55.000528662214684,\\"cutoff\\":509.2515887569149,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5249999999999999,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "0/1 -> 2/3: {\\"note\\":55.000528662214684,\\"cutoff\\":509.2515887569149,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5249999999999999,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "0/1 -> 2/3: {\\"note\\":64.00052866221468,\\"cutoff\\":509.2515887569149,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5249999999999999,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "0/1 -> 2/3: {\\"note\\":64.00052866221468,\\"cutoff\\":509.2515887569149,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5249999999999999,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "0/1 -> 2/3: {\\"note\\":64.00052866221468,\\"cutoff\\":509.2515887569149,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5249999999999999,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "1/3 -> 1/1: {\\"note\\":60.003688107962134,\\"cutoff\\":564.5418893373399,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5799038105676657,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "1/3 -> 1/1: {\\"note\\":60.003688107962134,\\"cutoff\\":564.5418893373399,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5799038105676657,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "1/3 -> 1/1: {\\"note\\":60.003688107962134,\\"cutoff\\":564.5418893373399,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.5799038105676657,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":59.010756146386846,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":59.010756146386846,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":59.010756146386846,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":59.010756146386846,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":64.01075614638685,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":64.01075614638685,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":64.01075614638685,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.5,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "2/3 -> 4/3: {\\"note\\":64.01075614638685,\\"cutoff\\":688.232561769837,\\"resonance\\":12,\\"gain\\":0.8,\\"decay\\":0.16,\\"sustain\\":0.5,\\"delay\\":0.2,\\"room\\":0.5,\\"pan\\":0.6,\\"s\\":\\"piano\\",\\"clip\\":1}",
+  "0/1 -> 1/1: {\\"note\\":33,\\"s\\":\\"sawtooth\\",\\"clip\\":1,\\"cutoff\\":300}",
+  "0/1 -> 1/1: {\\"note\\":33.12,\\"s\\":\\"sawtooth\\",\\"clip\\":1,\\"cutoff\\":300}",
+  "0/1 -> 1/2: {\\"s\\":\\"bd\\",\\"bank\\":\\"RolandTR909\\",\\"gain\\":0.5}",
+  "1/2 -> 1/1: {\\"s\\":\\"bd\\",\\"bank\\":\\"RolandTR909\\",\\"gain\\":0.5}",
+  "1/2 -> 2/3: {\\"s\\":\\"hh\\",\\"bank\\":\\"RolandTR909\\",\\"gain\\":0.5}",
+  "2/3 -> 5/6: {\\"s\\":\\"hh\\",\\"bank\\":\\"RolandTR909\\",\\"gain\\":0.5}",
+  "5/6 -> 1/1: {\\"s\\":\\"hh\\",\\"bank\\":\\"RolandTR909\\",\\"gain\\":0.5}",
+]
+`;
+
 exports[`renders tunes > tune: barryHarris 1`] = `
 [
   "0/1 -> 2/1: {\\"note\\":\\"C3\\",\\"clip\\":1,\\"s\\":\\"piano\\",\\"release\\":0.1,\\"pan\\":0.4722222222222222}",
diff --git a/repl/src/tunes.mjs b/repl/src/tunes.mjs
index 1b09a977..fcb7b4db 100644
--- a/repl/src/tunes.mjs
+++ b/repl/src/tunes.mjs
@@ -818,3 +818,21 @@ stack(
   ,
   s("bd*2,[~ hh]*2,~ cp").bank('RolandTR909')
 )`;
+
+export const arpoon = `// licensed with CC BY-NC-SA 4.0 https://creativecommons.org/licenses/by-nc-sa/4.0/
+// "Arpoon" by Felix Roos
+await samples('github:tidalcycles/Dirt-Samples/master')
+
+"<<Am7 C^7> C7 F^7 [Fm7 E7b9]>".voicings()
+  .arp("[0,3] 2 [1,3] 2".fast(3)).legato(2)
+  .add(perlin.range(0,0.2)).sub("<0 -12>/8")
+  .note().cutoff(perlin.range(500,4000)).resonance(12)
+  .gain("<.5 .8>*16")
+  .decay(.16).sustain(0.5)
+  .delay(.2)
+  .room(.5).pan(sine.range(.3,.6))
+  .s('piano').clip(1)
+  .stack("<<A1 C2>!2 F2 [F2 E2]>".add.out("0 -5".fast(2)).add("0,.12").note().s('sawtooth').clip(1).cutoff(300))
+  .slow(4)
+  .stack(s("bd*4, [~ [hh hh? hh?]]*2,~ [sd ~ [sd:2? bd?]]").arp("0|1").bank('RolandTR909').gain(.5).slow(2))
+`;