diff --git a/packages/core/cyclistworker.js b/packages/core/cyclistworker.js
index b0028698..56af5531 100644
--- a/packages/core/cyclistworker.js
+++ b/packages/core/cyclistworker.js
@@ -7,7 +7,6 @@ let lastEnd = 0; // query end of last tick
 // let getTime = getTime; // get absolute time
 let num_cycles_at_cps_change = 0;
 // let onToggle = onToggle;
-let latency = 0.1; // fixed trigger time offset
 let interval = 0.1;
 
 //incoming
@@ -18,7 +17,7 @@ let interval = 0.1;
 // {type: toggle, payload?: {started: boolean}}
 
 //sending
-//{type: 'tick', payload: {begin, end, phase, time }}
+//{type: 'tick', payload: {begin, end, deadline }}
 //{type: 'log', payload: {type, text}}
 
 const getTime = () => {
@@ -34,7 +33,7 @@ const log = (text, type) => {
   sendMessage({ type: 'log', payload: { text, type } });
 };
 
-createClock(
+let clock = createClock(
   getTime,
   // called slightly before each cycle
   (phase, duration, tick) => {
@@ -53,7 +52,7 @@ createClock(
       lastEnd = end;
       const tickdeadline = phase - time; // time left until the phase is a whole number
       lastTick = time + tickdeadline;
-      sendMessage({ type: 'tick', payload: { begin, end, phase, time } });
+      sendMessage({ type: 'tick', payload: { begin, end, tickdeadline } });
     } catch (e) {
       log(`[cyclist] error: ${e.message}`, 'error');
     }
@@ -73,6 +72,33 @@ self.onconnect = function (e) {
   port.start(); // Required when using addEventListener. Otherwise called implicitly by onmessage setter.
 };
 
+self.onmessage = (message) => {
+  const { type, payload } = message;
+  switch (type) {
+    case 'cpschange': {
+      if (payload.cps !== cps) {
+        cps = payload.cps;
+        num_ticks_since_cps_change = 0;
+      }
+      break;
+    }
+    case 'toggle': {
+      const { started } = payload;
+      if (started) {
+        clock.start();
+      } else {
+        clock.stop();
+      }
+      break;
+    }
+    case 'requestcycles': {
+      const secondsSinceLastTick = getTime() - lastTick - clock.duration;
+      const cycles = this.lastBegin + secondsSinceLastTick * this.cps; // + this.clock.minLatency;
+      sendMessage({ type: 'requestedcycles', payload: { cycles } });
+    }
+  }
+};
+
 function createClock(
   getTime,
   callback, // called slightly before each cycle
@@ -84,6 +110,7 @@ function createClock(
   let phase = 0; // next callback time
   let precision = 10 ** 4; // used to round phase
   let minLatency = 0.01;
+
   const setDuration = (setter) => (duration = setter(duration));
   overlap = overlap || interval / 2;
   const onTick = () => {
@@ -115,6 +142,7 @@ function createClock(
     clear();
   };
   const getPhase = () => phase;
+
   // setCallback
   return { setDuration, start, stop, pause, duration, interval, getPhase, minLatency };
 }
diff --git a/packages/core/neocyclist.mjs b/packages/core/neocyclist.mjs
new file mode 100644
index 00000000..da2b7794
--- /dev/null
+++ b/packages/core/neocyclist.mjs
@@ -0,0 +1,73 @@
+import { logger } from './logger.mjs';
+
+const sharedworker = new SharedWorker(new URL('./cyclistworker.js', import.meta.url));
+sharedworker.port.start();
+
+export class NeoCyclist {
+  constructor({ onTrigger, onToggle, latency = 0.1, onError }) {
+    this.started = false;
+    this.pattern;
+    this.onToggle = onToggle;
+    this.latency = latency;
+    this.worker = new SharedWorker(new URL('./cyclistworker.js', import.meta.url));
+    this.worker.port.addEventListener('message', (message) => {
+      const { payload, type } = message;
+      switch (type) {
+        case 'tick': {
+          console.log('tick');
+          const { begin, end } = payload;
+          const haps = this.pattern.queryArc(begin, end);
+          haps.forEach((hap) => {
+            if (hap.part.begin.equals(hap.whole.begin)) {
+              const deadline = (hap.whole.begin - begin) / this.cps + payload.deadline + latency;
+              const duration = hap.duration / this.cps;
+              onTrigger?.(hap, deadline, duration, this.cps);
+            }
+          });
+          break;
+        }
+        case 'log': {
+          const { type, text } = payload;
+          if (type == 'error') {
+            onError(text);
+          } else {
+            logger(text, type);
+          }
+        }
+      }
+    });
+  }
+  sendMessage(type, payload) {
+    this.worker.port.postMessage({ type, payload });
+  }
+
+  now() {
+    this.sendMessage('requestcycles', {});
+  }
+  setCps(cps = 1) {
+    this.sendMessage('cpschange', { cps });
+  }
+  setStarted(started) {
+    this.sendMessage('toggle', { started });
+    this.started = started;
+    this.onToggle?.(started);
+  }
+  start() {
+    logger('[cyclist] start');
+    this.setStarted(true);
+  }
+  stop() {
+    logger('[cyclist] stop');
+    this.setStarted(false);
+  }
+  setPattern(pat, autostart = false) {
+    this.pattern = pat;
+    if (autostart && !this.started) {
+      this.start();
+    }
+  }
+  log(begin, end, haps) {
+    const onsets = haps.filter((h) => h.hasOnset());
+    console.log(`${begin.toFixed(4)} - ${end.toFixed(4)} ${Array(onsets.length).fill('I').join('')}`);
+  }
+}
diff --git a/packages/core/repl.mjs b/packages/core/repl.mjs
index 245b651f..b3b810c0 100644
--- a/packages/core/repl.mjs
+++ b/packages/core/repl.mjs
@@ -4,6 +4,7 @@ import { logger } from './logger.mjs';
 import { setTime } from './time.mjs';
 import { evalScope } from './evaluate.mjs';
 import { register, Pattern, isPattern, silence, stack } from './pattern.mjs';
+import { NeoCyclist } from './neocyclist.mjs';
 
 export function repl({
   interval,
@@ -52,11 +53,21 @@ export function repl({
     onUpdateState?.(state);
   };
 
-  const scheduler = new Cyclist({
+  // const scheduler = new Cyclist({
+  //   interval,
+  //   onTrigger: getTrigger({ defaultOutput, getTime }),
+  //   onError: onSchedulerError,
+  //   getTime,
+  //   onToggle: (started) => {
+  //     updateState({ started });
+  //     onToggle?.(started);
+  //   },
+  // });
+
+  const scheduler = new NeoCyclist({
     interval,
     onTrigger: getTrigger({ defaultOutput, getTime }),
     onError: onSchedulerError,
-    getTime,
     onToggle: (started) => {
       updateState({ started });
       onToggle?.(started);