Bruno is 23 years young. A party is being thrown not only to celebrate birth, but to acknowledge all friends under a roof with Bruno's favorite DJ. Drinks are pretty damn cheap. The music will be out of sight. All are welcome. There is a cover because DJ's need to get paid.
For physical events that happen at a specific time. For example a concert, or dance performance. If there are multiple shows, you can still duplicate your event to cover them all.