Stuff that is with a bank or financial institution is safe, at least from theft. CDs? lawls that would be a pain to manage. How much is a typical music album on CD worth these days? I mean sure you could get some rare or limited edition stuff if you're into it and want to have it on hand as emergency fund but I would not actually go out and buy CDs just to "store" money. I would do gold before CDs, you can either buy the gold and have it, or I think you can also buy it "on paper" like stocks. The stock way is safest from theft but it's not really real so not sure what happens in a serious situation like the entire financial system crashing. Then again regular bank accounts would be gone too. I imagine the odds of that is super slim though, I would hope they have good backups.
Either way if you're really paranoid a good thing is to just have several stashes at different banks in different formats. Like liquid cash in one bank, mutual funds in another etc.
Having some cash at home is probably not a bad idea either. I really should do that myself. Maybe a grand stashed in a really safe spot. Basically if there is an oddball situation where the bank system is temporarily down for a week or something at least you have cash on hand for purchases. The odds of that are probably super slim though. In a situation like that my worse fear would be auto pay bills not being processed and my utilities being shut down or my house being repoed, not my inability to buy stuff at a store. I can't imagine the banking system going down for that long though.