Once you file a dispute, the claimant has UP to 30 days to respond. Possible scenarios:
1) They don't take an action at all and 30 days later the claim gets dropped automatically.
2) They agree with the dispute and manually drop the claim....any time within that 30 days period.
3) They disagree and then you receive a strike. At that point, even if you were completely in the right (and you are as you're playing 300 years old pieces!), you can't really get much help from YouTube anymore. It's up to you if you want to lawyer up and file a DMCA.
That's my my understanding, but I could be wrong. I've received over 50 claims for 'In The Mix' channel. Sometimes multiple copyright claims for the same video. Only a few disputes (such as the one for The Lark/Glinka) were reviewed by the claimant. The rest went through that 30 days period and expired on their own.