: Complete the course (any song/difficulty/mod) and watch the end credits. Everything will then be available for use. Key Game Content Total Songs
A very specific topic!
Empress has a famous bug where the game runs at double speed on modern systems. The best ISO fix involves enabling "Enable Cheats" and using the aforementioned .pnach file to cap the frame buffer. A truly "best" ISO guide will mention this fix explicitly. beatmania iidx 16 empress iso best