Buy a bandana as a ticket for 2000 yen, which is a pass to all the lives held at 17 bars/restanrants. Your drinks/foods are not included. Your ticket fee will be donated to Iwate, Miyagi, Fukushima, which are prefectures damaged in the series of earthquakes and tsunamis last year.
The restaurants, the bars, the bands have been working hard to make this event happen, for nearly free, if you think about their time and fees to prepare bandanas, equipments and stuff. There are sponsors contributing money for the event, for the whole 2000 yen will be sent to the prefectures.
So if you buy a few drinks, you can also contribute to the bars/restaurants, and be part of it! Just enjoy the lives and you can change Japan a bit in a positive way. I believe it's more important than just donating money.