Fix looping sources having a pan slider

src/audio.ts

@@ -45,9 +45,6 @@ export abstract class Source extends Node {
   @exposedNumber("Volume", 0, 1)
   public volume = 1;
 
-  @exposedRange("Panning", -1, 1)
-  public panning: [number, number] = [-0.2, 0.2];
-
   constructor(name: string) {
     super(name);
     this.gain = context.createGain();
@@ -76,6 +73,9 @@ export class IntervalSource extends Source {
   @exposedRange("Interval", 0.25, 30)
   public interval: [number, number] = [1, 5];
 
+  @exposedRange("Panning", -1, 1)
+  public panning: [number, number] = [-0.2, 0.2];
+
   private remaining = 0;
 
   private started = false;