Japanese-Portuguese dictionary by Jesuit missionary
I found this by chance while looking for Historia de Iapam. This is Arte da Lingoa de Iapam, Japanese-Portuguese dictionary edited by Iago Rodoriguez, a Jesuit missionary in Nagasaki in 1604.
In this dictionary, I couldn't find any words similar to "ongaku", music in modern Japanese. Instead, I could find words such as sarugaku, quangen (kangen in current Japanese), tsuzumi uchi, taiko uchi and fuye fuki (fue in current Japanese).
A part kangen which is instrumental music without dance in gagaku, it is not written a word for instrumental ensemble for popular music. Rather, it seems that people recognise as individual instrumentalist as drammer (tsuzumi or taiko), or flutist.