Firms in which market structure hold the most market power?

The answer is monopoly.

Monopoly is the firms in which market structure hold the most market power

Explanation:

in this scenario it would be the consumer demand as most influential in making the decision. the band members need to figure out where and from whom they will make the most money, in other words who out of the two consumer groups - football fans or car drivers - will spend their money, who is more likely to contribute to their cause and buy what they are offering.