This may seem like a pretty stupid question, but I don't have much experience playing from a lead sheet. What do chords that are in parenthesis mean?
Exactly as stated above. They are implied by the melody, but it's not necessary to hit them.
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i think i means play those chords the 2nd time through, the ones that aren't parenthesized play the first time through
As it's already been stated 3 times, it means that the chords are implied by the melody, or are being played by the pianist. So basically, play them if you feel like it.
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