I just got a TC Quintessence harmony pedal, and I was surprised to learn how it creates third-above harmony notes when set to the natural minor scale. The idea of the effect pedal is to create harmony voices for any notes fed to the input, and this is done by specifying a scale and one or two intervals, for example C natural minor and a 3rd up. This is simple and works as expected, as long as the input follows the set scale. However the input doesn't have to be restricted to the specified scale, and the pedal will produce something for notes outside the scale as well. For the example of a 3rd above in C natural minor ("aeolian"), the note mapping goes like this: (not caring about enharmonic spellings)

  • input:C, harmony:Eb
  • input:C#, harmony:E
  • input:D, harmony:F
  • input:Eb, harmony:G
  • input:E, harmony:Ab (!? why not G?)
  • input:F, harmony:Ab
  • input:F#, harmony:A
  • input:G, harmony:Bb
  • input:Ab, harmony:C
  • input:A, harmony:C# (!? why not C?)
  • input:Bb, harmony:D
  • input:B, harmony:Eb (!? why not D?)

My question is, is there a music-theoretical justification for harmonizing E, A and B with major thirds like that? Is there perhaps a style of music, a tradition or genre, where E, A and B would be harmonized with major thirds, if a minor key is assumed? Or is it just an arbitrary choice, perhaps for technical, not musical reasons. Because for practical situations it would be vastly more useful if E mapped to G instead of Ab, so that it would harmonize well in melodies that temporarily use C major and an E melody note, which is a common pattern. And if A mapped to C and B mapped to D, the same scale would somewhat support melodies using harmonic and melodic minor as well as natural minor. The mappings for C# and F# are actually good, because a C# is quite often used in a C#dim7/C -> Fm motion or C7b9 chord, and F# is often used e.g. in a D7 -> G7 motion.

The way E, A and B are currently programmed, it's hard to come up with any song or practical situation where those harmonies would make sense. But maybe they make sense in theory, and there's just something I don't understand? I've been trying to get my head around the "TonePrint" programming thingy, and I'm feeling that maybe I just don't understand the theory. They have all sorts of fancy scales like "Super Locrian", but these are not really explained anywhere, and playing out-of-scale notes usually produces musically meaningless harmonies.

Why I suspect there might be a theoretical justification for why my idea might be better is, the "bad" notes are exactly those ones that are flattened compared to C major. C minor has three flats: Bb, Eb and Ab. And the way TC has handled the out-of-scale notes, each of them is mapped to the previous lower in-scale note's harmony, plus one semitone. But that's not very musical IMO. Another interesting thing to notice is that all of the bad notes are major thirds (or four semitones). If those were minor thirds, then all five out-of-scale notes would be better harmonized with minor thirds above. Maybe in the style of music I'm playing, the only reason to use non-diatonic notes is to imply a diminished chord? Looking at the reasons why I'd like to have it that way, is exactly that - in pop melodies I use out-of-scale notes almost exclusively to do a dominant (or predominant) and then a dim chord is the right thing to use, thinking that D7 ≈ F#dim etc.

(Also feel free to tell if you know of other harmonizers where a third-above in a minor scale works or can be made to work like I explained)

Edit. I asked about this from TC Behringer's support, and after a couple of rounds of getting irrelevant copy-pasted text from user manuals they said that the behavior cannot be changed and that's it. Well OK, the customer support person was about a light-year away from being able to give any sort of musical justification for why the pedal does what it does.

For comparison I tested the competing (decade-old) Boss PS-6 pedal at a music store, and its handling of the five non-diatonic notes in "minor key" mode was not 5/5 either. And its sound quality is like a generation behind. So far I haven't found any sensible reasons behind any of this stuff. Probably they just didn't think about the whole thing.

Edit. I recently bought a small and cheap Zoom G1X Four multi-effect, which has, in addition to amp and cabinet models, practically all sorts of guitar effects, including a harmonic pitch shifter "HPS". The HPS effect adds one harmony voice according to the set key and scale/interval, and it sounds perfectly fine. Maybe not as buttery smooth as the Quintessence, but as good as the Boss PS-6 or better. But noticeably, the Zoom HPS effect has an "m" minor scale mode, which handles ALL 12 chromatic notes perfectly, with exactly the right harmonies for non-diatonic notes, 5/5 points for Zoom. Maybe Zoom's programmers are more into regular traditional pop music and less into modal jazz. And the Zoom G1 Four, without the X expression pedal, costs only half of the price of the TC Quintessence.

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    Comment only! Used to work with a band whose singer used a vocal harmoniser. It could be set to one key for one song. Fine when all the harmonies were daiatonic, but let us down when, for instance, in key C, there was a D chord. That needed F# but the machine always gave F nat. Not a lot of use! Later machines use a guitar input, which they analyse what chord is played at the time, and adjust accordingly. Maybe that's a better bet for you?
    – Tim
    Commented Feb 2, 2020 at 11:50
  • @Tim this pedal is not for vocal harmonies, and the "pick the closest chord note" style of harmonisation isn't what I'm after. :) Commented Feb 2, 2020 at 14:55
  • Superlocrian is 7th mode of melodic minor thus not that fancy. It's actually very popular scale choice for altered dominant chords. Commented Oct 27, 2020 at 20:23
  • The major third above E is G♯, not A♭. A♭ is a diminished fourth above E.
    – phoog
    Commented Apr 11, 2021 at 22:56
  • @phoog That is correct. But since the device in question doesn't explicate its enharmonic spellings, its harmony note is heard as Ab, which I tried to highlight here. Or perhaps TC Behringer decided that a pitch one semitone above Eb must be an F flat? In any case, their choice of harmonization is musically nonsensical. Commented Apr 12, 2021 at 3:03

2 Answers 2


" ... if E mapped to G instead of Ab, so that it would harmonize well in melodies that temporarily use C major ... "

My first thought was it makes good harmony to tonicize the F minor chord. Regardless, your suggested harmonization makes sense to me E G, A C, and B D as they form obvious chords in minor key harmony, respectively V6/iv, IV6, and V6.

Harmonizing in major third would provide secondary dominants to chords in the parallel major key: V/vi, V/ii, and V/iii respectively. Secondary dominants to borrowed chords seems a bit obscure for harmonizing in minor.

Looking for some explanation I suppose you need to look at it linearly instead of harmonically (ironic for a harmonizer.) I sketched out the harmonization like this...

input:C, harmony:Eb
        input:C#, harmony:E ------------------ E rise half step from Eb, E half step below F
input:D, harmony:F
input:Eb, harmony:G
        input:E, harmony:Ab (!? why not G?) -- Ab rise half step from G, Ab anticipates next Ab
input:F, harmony:Ab
        input:F#, harmony:A
input:G, harmony:Bb
input:Ab, harmony:C
        input:A, harmony:C# (!? why not C?) -- C# rise half step  from C, C# half step below D
input:Bb, harmony:D
        input:B, harmony:Eb (!? why not D?) -- Eb rise half step from D, Eb anticipates next Eb

...it seems the idea is when a chromatic tone is played for the input it is harmonized with a tone one half step above the previous diatonic harmony tone.

Rather than a bona fide harmonic approach it seems to be a linear approach to use chromatic half steps between diatonic tones.

  • I thought about this and it feels plausible for an engineer way of thinking - if the input pitch rises, the output pitch should rise as well? I would suppose that someone must have thought about it at least for half a second when having to fill a table with numbers. ;) But still, e.g. during an E - > F step, when the previous note is non-diatonic, then the harmony output does not change... Anyway, I think my suggested notes would create harmonies that naturally support a minor tonality, letting one play even chromatic notes and get a meaningful common-sense harmony for the selected tonic. Commented Oct 27, 2020 at 22:01
  • I think it's a tricky business to take only one tone for input and then harmonize. After some time learning about figured bass/rule of the octave, I realize two tones with direction a really needed to get a minimal context. Of course pedals like this surely have rock music in mind, so it's a different harmonic game. Commented Oct 28, 2020 at 17:00

This is arbitrary. The highlighted notes don't belong to the scale, so the corresponding chord must be non-diatonic. They had to make some assumptions. For the A, A-C# suggests A7 chord which is a secondary dominant to Dm. For the other notes... do they mean secondary dominant chain B7→E7→A7→Dm? Maybe B–Eb could be Cminmaj7, thus borrowed from melodic minor? Or G7#5?...

I agree, that wouldn't be the first choice I would think of. Also, miserable support. Perhaps you can still return the pedal? (edit, oh now I see your post is 8 months old...)

Maybe you need a more advanced unit. Some other TC models can "sense" the band harmony from an instrument input, or in built microphone. Probably there are also available products from competing companies. I'm quite sure there are units allowing you to play the harmony notes on another instrument, but I can't remember specific names.

  • The support wasn't that bad, at least they openly said that they won't change the product. ;) But yes, the more I think about this, it feels that the cases where a major third harmonization would work are further away in a circle-of-fifths sense, A -> D -> G, when a minor third fits in situations that are only one step away. One real-life scenario for a major third that comes to mind is something like harmonizing a non-diatonic Db with F in a Bbm6 - C7 - Fm sequence, which is quite often used in Cm. But that only works during the Bbm6, and over C7 the Db would need a minor third again. Commented Oct 27, 2020 at 21:49
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    FWIW, the dirt-cheap Zoom G1 Four multi-effect pedal has a harmonizer effect "HPS", which has a minor scale mode "m" that harmonizes with a third above exactly the way I want! I was really surprised to find that in the cheapest multieffect out there. Commented Apr 11, 2021 at 20:22

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