Feat: polyphony + iterator reset

tests/forth/sound.rs

@@ -106,3 +106,35 @@ fn param_only_multiple_params() {
     assert!(outputs[0].contains("gain/0.5"));
     assert!(!outputs[0].contains("sound/"));
 }
+
+#[test]
+fn polyphonic_notes() {
+    let outputs = expect_outputs(r#"60 64 67 note sine s ."#, 3);
+    assert!(outputs[0].contains("note/60"));
+    assert!(outputs[1].contains("note/64"));
+    assert!(outputs[2].contains("note/67"));
+}
+
+#[test]
+fn polyphonic_sounds() {
+    let outputs = expect_outputs(r#"440 freq kick hat s ."#, 2);
+    assert!(outputs[0].contains("sound/kick"));
+    assert!(outputs[1].contains("sound/hat"));
+}
+
+#[test]
+fn polyphonic_cycling() {
+    let outputs = expect_outputs(r#"60 64 67 note 0.5 1.0 gain sine s ."#, 3);
+    assert!(outputs[0].contains("note/60"));
+    assert!(outputs[0].contains("gain/0.5"));
+    assert!(outputs[1].contains("note/64"));
+    assert!(outputs[1].contains("gain/1"));
+    assert!(outputs[2].contains("note/67"));
+    assert!(outputs[2].contains("gain/0.5"));
+}
+
+#[test]
+fn polyphonic_with_at() {
+    let outputs = expect_outputs(r#"0 0.5 at 60 64 note sine s ."#, 4);
+    assert_eq!(outputs.len(), 4);
+}