Generally speaking, 'a festival of art' would be considered an incorrect phrase. Rather, it's a festival of the arts OR an arts festival - given that there are many facets to art, and the term an arts festival would generally be the relevant term given the suggested art form a guitar recital would generally be considered to form a part of a greater series of musical and/or visual art forms. (I think I wrote an answer that sounds more like AI than I've ever sounded before. 😬) Oh yes, American English increasingly uses 'on' for everything where the Brits use 'at'. I cover all these and much more highbrow and exotic themes with my polyglot polymath level students. Is that you?