6 digidrum instruments are included in the internal ROM of the soundchip.
Also be aware that despite the naming similarities, the OPN3 and OPL3 soundchips are entirely incompatible with each other.
Relevant datasheets: [[Media:YMF288.pdf|OPN3 (ymf288) (Japanese)]] and [[Media:YM2608J Translated.pdf|OPNA (ym2608) (English)]]