MIDI Murder Box is the first unlockable stage in Soundodger+. The song is made with the "MIDI" music creating tool & is composed of 8-Bit chip noises. It has no vocals.
The major thing that sets this stage apart from other stages in the fact that it is the only stage in the game with one single enemy. The only stage that has something like this is Waves From Nothing that is mostly one non-moving enemy but has other enemies active for a small portion.
Because it has only 1 enemy, it is very easy. The developer probably used it as a fun experiment.