All spatial audio demos should play Shostakovich Symphony No. 5, second movement. It's got lots of instruments with isolated parts, challenging dynamic range, but mostly it's a just blast.
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I would like to see them try this Danny Kaye scene from The Secret Life of Water Mitty, in which he recreates a symphony, in any audio demo. It might not have challenging dynamic range, but his imitations of instrustments is amazing.

