Is it illegal to videotape a concert?
In a word, yes. If you happen to have written the song(s) that the band is performing, then no; any type of copyright infringement is illegal, and presuming that you will not be paying royalties to the copyright holder(s), you will be infringing copyright. However, certain bands such as The Grateful Dead have historically allowed their concerts to be taped, although now in order to do so one must have a special "Taper Ticket"