Hi svennysvensen-
Sorry to hear you're having issues with Octavox MIDI control in Logic X.
MIDI control of plug-ins in Logic is a bit confusing. You need to create a new instrument track, and select Octavox as the instrument (it wll be listed under AU MIDI-Controlled Effects->Eventide->Octavox). Then, select the track who's audio you want to process in the Sidechain menu in the top right of the plug-in window. Now, if you have the instrument track selected, you should be able to play/record MIDI notes affecting the source audio.
Let me know if that doesn't solve your issue.
Best,
Tom
