What am I hearing???

~~~~Hello,
I hope someone can explain why on some cd's the long piano notes sound slightly warbled. Not the normal vibration from the piano's wires. Am I hearing laser trying to track info on a non-concentric disc? I noticed a lot of cd's data area slightly non-concentric to edge of disc. Shouldn't the laser be able to trace imperfections? Warranty time? Starting to bug me, RATS!

Just The Facts
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