You may accept the donation, but it is not deductible by the donor as a charitable contribution because it is earmarked for the benefit of a specific individual. You should not give the normal charitable contribution receipt for the gift because of that.

 

If you do pass it on to the conductor, it appears that you recognize that it is additional compensation on which taxes must be withheld, etc.

 

Whether it is appropriate or not is a question to which I don’t think there is an absolutely right or wrong answer. In general, I don’t like transactions that appear to be something (a charitable contribution) that they are not, and which make it easier for the donor to claim a deduction that is not legitimate. (A donor who gives a check for less than $250 doesn’t need your acknowledgment letter to claim the deduction.) On the other hand, if you were longing to pay the conductor more but simply don’t have the funds, this may be a serendipitous way to accomplish your goal.