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I doubt this is fast enough for quality data transfer and that laser and photodiode is probably not fast enough to operate in the MHz stably. I would recommend an avalanche photodiode and an IR laser diode (850nm or 1310 nm).
I don't think that LDR is well-suited on such speeds, its response time is too slow to have quality sound. I would recommend a photodiode, or for simplicity, a small solar panel found in most calculators, it will work even better.