Oslo has a very reputable jazz scene and offers countless bars, cafés and nightclubs to choose from.
There is a large number of places that offer live music, especially on weekends. Most bars and nightclubs downtown are open until around 3 am.
Many places that serve food during the day, turn up the volume at night and become more of a nightclub, with cocktails and DJ's. While everyone may enter during the day, the same place may practice age limits of 18, 20 or 25 at night.
Read more about restaurants and night life in Oslo.