I don't have the full Little Musician curriculum yet, but I know my LO gets bored and distracted if I repeat other lessons (like Tweedlewink) more than 1 or 2 times. As the pp mentioned, they may get bored and not enjoy the lessons if you repeat them. Also, you're only 10 (probably more by now) lessons into the program. Over time, they are likely to improve those listening skills so that they can identify correctly. It's great that they're trying! If you really think the older one is confusing the younger one, maybe you can show the lessons separately? Although, I think it's probably more fun for them to do the lessons together
good luck!