The Midi mode can be accessed from all other modes with the View > Midi menu option.

The current mode -- Chord, Table or Melody -- active when using this menu option, is the one that the program will return to when exiting Midi with the exit midi button. 

A faster way to go to the Midi Mode is to first click on the "goto player" button -- every other mode has this button --, and then when in Player mode click on the "goto midi" button.

There are two ways to leave the Midi mode.

One is to click on the "exit midi" button, this will return to whatever mode prompted the midi mode, and,

Click on the "goto player" button, this will land you in the Player mode.  See Midi and the Player.