Konami's KEY and APPEND DISC for PlayStation 1 and Dreamcast

During the 90's era, when Konami released their very first BEMANI game for the PlayStation 1, the beatmania in October 1998. The game consist of two disc, the Arcade disc and Yebisu Mix disc. The arcade disc is the direct version of beatmania in the arcade, while the Yebisu Mix act as APPEND disc. In order to play the Yebisu Mix, they must first load the arcade disc, select the DISC CHANGE option and swap disc. 

A Note in the cover art that the game requires a KEY DISC to play (cover art from pop'n music 4 APPEND)

The kind of concept was used up to APPEND ClubMIX, succeeding beatmania games were standalone game. If someone tries to load the APPEND DISC directly, a warning will appear in the screen and the game will not boot. pop'n music used this to their APPEND 3 and 4 (pop'n music 2, 5, and 6 as KEY DISC, GUITARFREAKS to their APPEND 2ndMIX (GUITARFREAKS 1st as KEY DISC). As for DanceDanceRevolution (DDR), they used this kind of setup to their CLUB VERSION's VOL. 1 and 2 (using the DDR 2ndReMIX and DDR 3rdMIX (CS) games). I previously blogged about CLUB VERSION DISC. They also implement the DISC CHANGE in its Dreamcast version of pop'n music.

DISC CHANGE schematics for beatmania 6thMIX + CORE REMIX (CS)

Interestingly, beatmania APPEND DISC can play the Bonus edit, more like an alter ego of the direct arcade port. They can play the Bonus edit if they DISC CHANGE in a certain order, for Example, in order to play the beatmania 5thMIX Bonus edit, they must load the beatmania Arcade disc, swapped disc to APPEND 3rdMIX, then, swap disc from APPEND 3rdMIX to APPEND 5thMIX. Another interesting feature by using the DDR 3rdMIX (CS) as KEY DISC for DDR 1st and 2ndReMIX the graphic interface of the latter will be used and not the original interface, although, background animations are disabled during gameplay.