Tip: Layer 3 backgrounds and tides disappear when you hit a message box, so plan your level around that. For example, you can add a sublevel without layer 3 at the start/midpoint, and include your message there.
Am I missing something as to why you include intro commands in front of each channel? That's an extra 12 bytes I don't see use for. Without them it sound the same so I don't know but I still left them. Feel free to update it again if you'd like or simply message me and I'll edit it since it's only one small edit.