diff --git a/packages/core/signal.mjs b/packages/core/signal.mjs
index a6868937..d8460e17 100644
--- a/packages/core/signal.mjs
+++ b/packages/core/signal.mjs
@@ -1,5 +1,5 @@
 import { Hap } from './hap.mjs';
-import { Pattern, fastcat, reify, silence } from './pattern.mjs';
+import { Pattern, fastcat, reify, silence, stack } from './pattern.mjs';
 import Fraction from './fraction.mjs';
 import { id } from './util.mjs';
 
@@ -101,4 +101,38 @@ Pattern.prototype._degrade = function () {
   return this._degradeBy(0.5);
 };
 
-Pattern.prototype.patternified.push('degradeBy', 'degrade');
+Pattern.prototype._undegradeBy = function (x) {
+  return this._degradeByWith(rand.fmap((r) => 1 - r), x);
+};
+
+Pattern.prototype._undegrade = function () {
+  return this._undegradeBy(0.5);
+};
+
+Pattern.prototype._sometimesBy = function (x, func) {
+  return stack(this._degradeBy(x), func(this._undegradeBy(1-x)));
+};
+
+Pattern.prototype.sometimesBy = function (patx, func) {
+  const pat = this;
+  return reify(patx).fmap((x) => pat._sometimesBy(x, func)).innerJoin();
+};
+
+Pattern.prototype._sometimesByPre = function (x, func) {
+  return stack(this._degradeBy(x), func(this).undegradeBy(1-x));
+};
+
+Pattern.prototype.sometimesByPre = function (patx, func) {
+  const pat = this;
+  return reify(patx).fmap((x) => pat._sometimesByPre(x, func)).innerJoin();
+};
+
+Pattern.prototype.sometimes = function (func) {
+  return this._sometimesBy(0.5, func);
+};
+
+Pattern.prototype.sometimesPre = function (func) {
+  return this._sometimesByPre(0.5, func);
+};
+
+Pattern.prototype.patternified.push('degradeBy', 'undegradeBy');