Gravesite Recitals

Professor Gerry Beyer at Wills, Trusts & Estates Prof Blog quotes a will clause here, which was sent to him by a lawyer in San Antonio, Texas, as follows:

The [Charitable Beneficiary] will have a group of people minimum of five (5), sing, anything they choose, in English, at my late wife's * * * gravesite, in the City Cemetery * * * at noon, every 27th day of the month, every month, in perpetuity whether it falls on Sundays or Holidays, for at least fifteen (15) minutes. The participants do not have to be professional singers or even be able to carry a tune.

If the group is unable to carry a tune, is this clause void as against public policy?