Summer Music Festival near Nozawa Onsen
Iiyama Sawagosa Music Festival
Big weekend coming up in nearby Togari. At the base of the ski resort there is cool little festival taking place on Sat 25/8 and Sun 26/8.
Think of Fuji Rock but much more intimate lots of locals and cool acts having a great time.
Just 3500 Yen entry and free on the Sunday
Here is a link for more details http://sawagosa.com/2017/