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ZPlane Tonic

Music Theory Assistance Plug-in By Paul White
Published February 2022

ZPlane Tonic plug-in

ZPlane’s Tonic is a plug‑in designed to work out the key of a piece of music and to suggest musical scales and chords that might work with it. It includes a very basic synthesizer and virtual keyboard that can be used to replay the suggested notes or to trigger one‑finger triad chords that fit with the scale. Tonic supports all the common plug‑in formats for Mac and Windows, including Pro Tools’ AAX.

Tonic is used as an insert effect on a track, bus or master and it can either do its thing in real time or you can set it to work on an audio file offline. For working out the key of a specific part, such as a sample loop or a guitar part, then it is best to load Tonic as an insert on that track. To figure out the key of an entire tune, then Tonic is best used as an insert effect on the master bus.

On launching Tonic, Realtime Mode is selected by default so all you need to do is play the audio and the analysis starts. Tonic shows three possible keys, with the shaded areas around the centre circular display showing the probability for each one. The key shown at the top is the most likely match. Sometimes the key of a piece of music isn’t obvious, perhaps because some notes are not used, or maybe because the odd ‘accidental’ falls outside the conventional scale — hence the alternative key suggestions. If there are any key changes, it’s best to break the song down into sections for analysis.

There are few user controls, but you can decide whether keys should be shown as sharps or flats and there’s a Reset button to clear previous data. Furthermore, if there’s a section of the tune that you know uses non‑key notes or that involves a key change, you can press the Pause button and anything ‘heard’ by the plug‑in will be ignored until you click back into Play mode. Similarly, if you just want to base the analysis on a specific section of music or perhaps a sample loop, you only need to play that section. If there are no ‘trick’ sections in the music, then it’s best to play the whole track. In use the displayed keys may change several times before settling down as Tonic accumulates more information from the audio so it is always best to play the longest extract possible unless there are key changes. The root pitch of A is also displayed, which is a help where the audio in question isn’t at concert pitch.

A Keyboard View can be opened at the bottom of the GUI, where the suggested scale notes (always seven) are highlighted on the virtual keyboard, and you can click on these to play the notes using the internal synth just to make sure they fit. A Fold Keys button displays only the keys containing valid pitches. Selecting the Chords button places seven compatible chords on single keys so you can play around with these to see if they match the song just by pressing the keys that correspond to the chords and if you use the Fold Keys button, then non‑chord notes are hidden. If the suggested chords don’t fit, then you can switch to one of the other two suggested keys to see if one of them works better.

Doing an off‑line analysis can yield faster results, but you still use the plug‑in — so you must first place an instance of Tonic on any DAW track. The File button at the top of the GUI can be used to switch to File Mode, at which point the Play button will change to a File Load button. The desired audio file is then located via a dialogue box, and the results will be displayed as per the real‑time mode. Again, beware of key changes that might fool this analysis.

Tonic worked very well for picking out either major or minor keys and the associated scale notes, and for suggesting main supporting chords too.

In practice Tonic worked very well for picking out either major or minor keys and the associated scale notes, and for suggesting main supporting chords too. It doesn’t seem to recognise exotic scale types but you can often get clues by also looking at the notes in the two ‘runner‑up’ scales. Being able to see any tuning offset is also very useful. As with its nearest counterpart, Antares Auto‑Key, Tonic takes a fair chunk of CPU overhead when active but that shouldn’t be an issue as once the key is known you would normally deactivate it. For those who can’t always figure out basic keys by ear Tonic is undoubtedly useful, especially when working with samples, loops or handling remixes, and it has the advantages of being inexpensive and very easy to use.


€39 (about $45).