add defaults and fanchor docs

packages/core/controls.mjs

@@ -753,6 +753,15 @@ export const { bprelease, bpr } = registerControl('bprelease', 'bpr');
  * .ftype("12db 24db")
  */
 export const { ftype } = registerControl('ftype');
+
+/**
+ * controls the center of the filter envelope. 0 is unipolar positive, .5 is bipolar, 1 is unipolar negative
+ * @name fanchor
+ * @param {number | Pattern} center 0 to 1
+ * @example
+ * note("{f g g c d a a#}%8").s("sawtooth").lpf("{1000}%2")
+ * .lpenv(8).fanchor("<0 .5 1>")
+ */
 export const { fanchor } = registerControl('fanchor');
 /**
  * Applies the cutoff frequency of the **h**igh-**p**ass **f**ilter.

packages/superdough/superdough.mjs

@@ -24,6 +24,12 @@ export function getSound(s) {
   return soundMap.get()[s];
 }
 
+const defaults = new Map([['fanchor', 0]]);
+
+export function setDefault(key, value) {
+  defaults.set(key, value);
+}
+
 export const resetLoadedSounds = () => soundMap.set({});
 
 let audioContext;
@@ -289,7 +295,7 @@ export const superdough = async (value, t, hapDuration) => {
     density = 0.03,
     // filters
     ftype = '12db',
-    fanchor = 0,
+    fanchor = defaults.get('fanchor'),
     // low pass
     cutoff,
     lpenv,