Master track modes and keys demystification in progress

In this topic I wish to gradually demystify modes, keys, chords, progressions etc. on the OP-Z master track. I am aware that information about music theory is widely available, but a lot of it is focused on guitars and/or much to dense for my limited span of attention. So here is what I found out, and on the bottom are some questions for you to answer and complete the demystification process for all.

  • Take an empty project (shift+project+stop to clear a project) and go to the CH track.
  • Make the note length 1 (hold track while turning green knob).
  • Enter the triad C-E-G on the first beat (hold the first beat button and press the notes in sequence).
  • Connect to the app and head to the Master track.
    First conundrum: you entered just about the most basic chord there is: the C major chord. But OP-Z thinks you are in the key of F and in C mixo (short for mixolydian) mode and there is a dial with an F on top with a sub dial pointing to V (roman numeral 5). Your OP-Z keys are lit and show C D E F G A bflat C.

OK, so I found out what this means and it took some digging, so I thought I’d share.

  • the mode name is equivalent to a roman numeral. There are seven modes, each with a pretty name, but also just a number.
  • the modes are easiest to understand if you play the notes on the keyboard: the first mode is Ionian and starts at C. That could be written down as C-i (roman numeral i). Play the same notes from the D key and suddenly you are playing in another mode: D-ii or D dorian. Etcetera gives you all seven modes (just don’t go to the black keys. There be dragons). I got this from this excellent walk that bass tutorial.
  • if you press a single key on the OP-Z you will transpose the song AND change its mode (and possibly its key).
  • if you press a single key that is lit, you will only change the mode. If you press an unlit key, you will change the key too.
  • if you play triads (with the root note at the bottom), you will be able to force the mode and change the key accordingly.
  • you can force ionian mode by entering a C-E-G-B chord. Then you will get the C key.

How is this useful?

  • if you play any of the notes that are lit in a lead, it will sound harmonious if you don’t change the key.
  • if you want a pleasant and simple progression, use a single finger to transpose the song and stick to the lit keys.
  • if you want more interesting stuff, go wild.
  • you can get a lot of the basic chord progressions with very little effort. But if you want anything more interesting (suspended, augmented, etc) you are on your own.
  • the fact that this can be sequenced makes OP-Z into a powerful tool for accompaniment. Added to the tilt-to-mic feature and this is a singing practicing dream.


  1. Why does OP-Z assume you want mixolydian F when you enter a Ionian C chord? Is it because of AC-DC songs (those apparently all are in mixo mode)?
  2. why does the mode have a name in the label on the right, but a number in the dial? Would it not have been more friendly to use the numerals everywhere (and switch to letters when there is a deviant)?
  3. what does a * mean next to the mode name?
  4. where to go from here?
  5. how does the OP-Z dial relate to thecircle of fiths? I see that it is similar, but what’s up with the rotating of the dial and the needle?

Nobody replied :frowning:

So how can I record a bassline (say C-C-Eb-E-G-C-A-G for example that is not stricly in C-major-dorian) while forcing the mater track to consider this as C-major-dorian for transposition?

If I record this bassline and then force the C-major-dorian on the master track by recording a step, it transposes my bassline.

Maybe I should accept whatever scale/mode it is choosing for me as my “root mode” and just find the number of half-tones I want to transpose by? But if I do that, I change the key (because I have to press one of the unlit buttons).

I have to say that this automatic system is really great when you want to improvise or create variations around something but if you want to manually control your transposition it’s problematic