fix reference error (sugarlabs#2534)

* fix reference error

* fix sugarlabs#2390

start beat events as soon as we encounter the on every beat do blok

* Revert "fix sugarlabs#2390"

This reverts commit 6e1319b.

js/turtleactions/RhythmActions.js

@@ -32,10 +32,10 @@ function setupRhythmActions() {
          * @param {String} blkName - note block type name
          * @param {Object} turtle - Turtle object
          * @param {Object} blk - corresponding Block object index in blocks.blockList or custom block number
-         * @param {Function} [_enqueue] - callback
+         * @param {Function} _enqueue - callback
          * @returns {void}
          */
-        static playNote(value, blkName, turtle, blk, _callback) {
+        static playNote(value, blkName, turtle, blk, _enqueue) {
             /**
             * We queue up the child flow of the note clamp and once all of the children are run, we
             * trigger a _playnote_ event, then wait for the note to play. The note can be specified