diff --git a/packages/shader/README.md b/packages/shader/README.md
index 851cc7814..42fc5a860 100644
--- a/packages/shader/README.md
+++ b/packages/shader/README.md
@@ -1,3 +1,16 @@
 # @strudel/shader
 
-Helpers for drawing shader
+Helpers for drawing shader.
+
+## Todos
+
+Here are the things that needs to be implemented:
+
+- [ ] Shader source error reporting
+- [ ] Shader import from url, like shadertoy or git
+- [ ] Display attribution
+- [ ] Compilation error reporting, e.g. to show the line number
+- [ ] Multiple instance and custom canvas position
+- [ ] Multiple program, to be swapped like a pattern
+- [ ] Texture inputs
+- [ ] Buffer inputs, e.g. to generate a texture
diff --git a/packages/shader/index.mjs b/packages/shader/index.mjs
index 41aa0e1de..931421e83 100644
--- a/packages/shader/index.mjs
+++ b/packages/shader/index.mjs
@@ -1,2 +1,2 @@
-export {loadShader} from './shader.mjs';
+export * from './shader.mjs';
 export * from './uniform.mjs';
diff --git a/packages/shader/shader.mjs b/packages/shader/shader.mjs
index e81a0cf50..8d9f0430c 100644
--- a/packages/shader/shader.mjs
+++ b/packages/shader/shader.mjs
@@ -59,7 +59,7 @@ const decayModulation = (decay) => {
 
 // Set an uniform value (from a pattern).
 export function setUniform(instanceName, name, value, position) {
-  const instance = _instances[instanceName || 'default'];
+  const instance = _instances[instanceName];
   if (!instance) {
     logger('[shader] not loaded yet', 'warning');
     return;
@@ -104,7 +104,8 @@ function setupUniforms(uniforms, program) {
       const uname = name.replace('[0]', '');
       const count = uniform.count | 0;
       if (!uniforms[uname] || uniforms[uname].count != count) {
-        // TODO: keep the previous value when the count change...
+        // TODO: keep the previous values when the count change:
+        // if the count decreased, then drop the excess, else append new values
         uniforms[uname] = {
           name,
           count,
@@ -174,6 +175,7 @@ async function initializeShaderInstance(name, code) {
         updateUniforms(instance.drawFrame, elapsed, instance.uniforms);
 
         instance.drawFrame.draw();
+        // After sometime, if no update happened, stop the animation loop
         if (instance.age++ < 100) requestAnimationFrame(instance.update);
         else instance.drawing = false;
       };
diff --git a/packages/shader/uniform.mjs b/packages/shader/uniform.mjs
index e1ae7f732..100b83b01 100644
--- a/packages/shader/uniform.mjs
+++ b/packages/shader/uniform.mjs
@@ -7,27 +7,75 @@ This program is free software: you can redistribute it and/or modify it under th
 import { register, logger } from '@strudel/core';
 import { setUniform } from './shader.mjs';
 
-export const uniform = register('uniform', (options, pat) => {
-  // Keep track of the pitches value: Map String Int
-  const pitches = { _count: 0 };
+/**
+ * Update a shader. The destination name consist of
+ *
+ * - the uniform name
+ * - optional array mapping, either a number or an assignment mode ('seq' or 'pitch')
+ *
+ * @name uniform
+ * @example
+ * s("bd").uniform("iColor")
+ * @example
+ * s("bd").uniform("iColors:seq")
+ * @example
+ * note("c3 e3").uniform("iMorph:pitch")
+ */
+function parseUniformTarget(name) {
+  if (typeof name === 'string')
+    return {name, mapping: 'single', position: 0}
+  else if (name.length == 2) {
+    const mapping = typeof name[1] === 'string' ? name[1] : 'single'
+    const position = typeof name[1] === 'string' ? null : name[1]
+    return {
+      name: name[0],
+      mapping,
+      position
+    }
+  }
+}
+
+// Keep track of the pitches value per uniform
+let _pitches = {}
+export const uniform = register('uniform', (target, pat) => {
+  // TODO: support multiple shader instance
+  const instance = "default"
+
+  // Decode the uniform defintion
+  const uniformTarget = parseUniformTarget(target)
+
+  // Get the pitches
+  if (!_pitches[uniformTarget.name])
+    _pitches[uniformTarget.name] = {_count: 0}
+  const pitches = _pitches[uniformTarget.name]
 
   return pat.onTrigger((time_deprecate, hap, currentTime, cps, targetTime) => {
-    const instance = options.instance;
+    // TODO: figure out how to get the desired value, e.g. is this pattern for pan, gain, velocity, ...
+    const value = hap.value ? (hap.value.gain || 1.0) : 1.0;
 
-    const value = options.gain || 1.0;
-    if (options.pitch !== undefined) {
+    // Get the uniform mapping position
+    let position = null
+    if (uniformTarget.mapping == 'pitch') {
+      // Assign one position per pitch
       const note = hap.value.note || hap.value.s;
       if (pitches[note] === undefined) {
         // Assign new value, the first note gets 0, then 1, then 2, ...
         pitches[note] = Object.keys(pitches).length;
       }
-      setUniform(instance, options.pitch, value, pitches[note]);
-    } else if (options.seq !== undefined) {
-      setUniform(instance, options.seq, value, pitches._count++);
-    } else if (options.uniform !== undefined) {
-      setUniform(instance, options.uniform, value);
+      position = pitches[note]
+    } else if (uniformTarget.mapping == 'seq') {
+      console.log("HERE", pitches)
+      // Assign a new position per event
+      position = pitches._count++
+    } else if (uniformTarget.mapping == 'single') {
+      // Assign a fixed position
+      position = uniformTarget.position
     } else {
-      console.error('Unknown shader options, need either pitch or uniform', options);
+      console.error('Unknown uniform target', uniformTarget)
     }
+
+    // Update the uniform
+    if (position !== null)
+      setUniform(instance, uniformTarget.name, value, position);
   }, false);
 });