Bug in completeMIX2 where previous song is played

Here’s the livestream that inspired this entry:

Even though they’re playing SYSTEM, all of the sudden you start to hear OPERATOR.

I thought “Maybe the mic is picking up sounds from another cabinet?” but apparently that wasn’t the case.

Since OPERATOR was the last song they were playing before SYSTEM, was the previous song left behind?

Experiment to reproduce the bug

After the livestream ended, I performed an experiment to reproduce the bug under the same conditions.

After playing OPERATOR (A), play SYSTEM (A).
The options to use are BATTLE and no HI-SPEED.

I easily reproduced it.

Conditions for the bug to happen

As I tested the game out while changing around the options and songs, the conditions for the bug to happen started to become a little more clear:

  • The previous song can be anything (the difficulty doesn’t matter, either)
  • It won’t happen unless the next song is the Another chart for SYSTEM
  • It won’t happen without the BATTLE option
  • It won’t happen if you use a HI-SPEED?
  • It won’t happen unless both players are hitting the keys?
    (It didn’t happen when one or both players ignored the keys)
  • It won’t always happen in the same place
    (Even if you play the same song, it sometimes happens at a different spot)
  • It only happens on actual hardware?
    (Apparently won’t happen in an emulator)
A video I received of someone testing it in an emulator

There could be songs other than SYSTEM where the chart plays the previous song, so this is something to research in the future.