They make and sell traditional musical instruments (flutes, drums, stringed instruments, etc.) from various parts of Indonesia. The shop is in the owner's house, and he is very friendly - just drop by and you can see and try the instruments he has on display. If you want to buy, however, you will have to make a custom order, as the instruments on display are not for sale. The prices are pretty good, starting at tens of thousands of rupiah for the cheaper flutes to hundreds of thousands for stringed instruments.