Cal. Gov't Code § 25559
The board of supervisors may:
(b) Appropriate and expend money from the fund raised by special tax to exploit the resources of the county, and commonly known as the “Exploitation fund,” to furnish music, either inside or outside the boundaries of the county, by entering into contracts, with or without competitive bidding, with individual musicians, orchestra, symphony associations, bands, or any other organization or corporation maintaining a band, orchestra, or other musical group for the purpose of furnishing free concerts to the public.
The provisions of this section shall be applicable only to boards of supervisors of counties having a population of nine hundred thousand or over, as ascertained and determined by state law.