1

Understanding the Fundamentals of Music (2006), by Robert Greenberg, B.A. in music (magna cum laude) from Princeton, Ph.D. in music composition from the University of California, Berkeley. p. 54 of the Lecture Transcript.

Any given major key contains only one tritone. It's the interval between the fourth and seventh scale-degrees. In the key of C major, for example, the tritone occurs between an F (the fourth scale-degree) and a B (the seventh scale-degree). Now, because there are 12 different major keys and only six different tritones, the tritones are doubled up: the same tritone will serve two different major keys. So, what major key does C major share a tritone with? The answer: the key of F# major, the major key farthest away from C major, the major key a tritone away from C major! My friends, keys a tritone apart will share the same tritone! (For our information, in F# major, the tritone occurs between B, which is the fourth degree of F# major, and E#, which is enharmonic with F, which is the seventh degree of F# major.) Dang, don't we just love the chromatic collection! The metaphors it presents us with are endless: The end is the beginning, the beginning is the end; opposites unite into singularities and singularities become opposites; all points are connected within the continuum. It's a fantastic system!

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Why can a given major key contain only 1 tritone?

  1. I don't understand why the "only one tritone" must be "the interval between the fourth and seventh scale-degrees"?

  2. I added to Greenberg's figures. In the left figure, why can't C-F# be another tritone for C maj? In the right, why can't F#-C be another tritone for F# maj?

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  • 1
    I didn't answer your question directly in my answer. You can add a tritone to any scale if you want to, but the lecture is specifically talking about staying in the diatonic pattern of each scale, so you wouldn't have the F# in C major's regular notes, and you wouldn't have the C in F#major's notes normally. – Alphonso Balvenie Jul 2 at 5:24
  • Yes, between the 4th and 7th notes of a majors scale is a tritone. There's also another (in a different place!) between the 7th and 4th notes. – Tim Jul 2 at 6:45
  • 1
    @Tim yes, the tritone inverts to itself. – Alphonso Balvenie Jul 2 at 7:40
  • 1
    for more tritone fun, see tritone substitution: en.wikipedia.org/wiki/Tritone_substitution – Alphonso Balvenie Jul 2 at 7:42
  • 2
    @Tim Wouldn't that count as an inversion rather than a second tritone? – Your Uncle Bob Jul 2 at 9:56
7

The lecture transcript isn't particularly clear unless you already have an understanding of the topic.

What is being presented is this:

in the major scale pattern, the tritone (three whole steps between notes) only occurs between the 4th note and the 7th note of the scale, exampled by in C major the jump between F and B (f-g-a-b, three whole steps).

     1 2 34 5 6 78
     C-D-EF-G-A-BC
           w w w 

He then goes on to explain that even though we can create a major scale pattern off of any of the twelve tones, because of the nature of the tritone it only occurs between six note parings (he really means tones, not notes) in the twelve possible keys.

Keys a tritone apart share the same tritone (in pitch, not note sequence, he doesn't make that clear).

For example if I am in the key of C major, the tritone above the tonic is F#, which isn't in the scale, it is the note between C Major scale's 4th and 5th degree, or a tritone higher.

     C-D-EFF#G-A-BC
     1 2 34TT5 6 78

If I move to F# Major, the then tritone in F# Major is the 4th to the 7th again, or B to E#, which is the actual pitch of F, so the B - F tritone.

Looking at the two keys, C major and F# major they share the same pitch jump of the tritone F-B, B-F, even though they aren't named the same.

     1  2  34  5  6  78 
     F#-G#-A#B-C#-D#-E#F#
              w  w  w

The main confusion is probably that when considering the tritone we are talking about the specific frequency jump of three whole steps, independent of the enharmonic naming of the notes.

3

"Any given major key contains only one tritone. It's the interval between the fourth and seventh scale-degrees."

Perfectly correct, if we take 'any major key' to mean just the notes of a major scale. If we have only C,D,E,F,G,A,B,C to choose from, the only tritone is between F and B.

Yes, of course we can play a tritone above C, which will be F#. Very likely it won't even imply a modulation to another key, we will still, in a very real sense, be 'in C major'. I'm delighted that you recognise this fact! A lot of questions in this forum are based on the misapprehension that only 'notes in the scale' are 'allowed. But, in this case, we're talking JUST about the notes of the major scale

2

Interesting question that made me think. I'm a guitar player who had someone hand me a Circle of fifths chart years ago to help me understand some things about music theory. Now I just pulled out my Circle of fifths chart and looked at it again to see that for any key chosen, I can look directly across (180 degrees) the chart and find the tri-tone for that key, and I counted them and I'm seeing twelve of them. One for each key. I don't wish to put up an incorrect answer, but it is my understanding that the tritone is the center tone of the Octave and the only tone that stays the same interval when inverted. It is three whole tones (steps) from the tonic and three whole tones (steps) from the Octave. That's the definition I understand and I'm figuring twelve of them. Where's the fallacy in my understanding?

  • 1
    In the main question comments Tim and I have a discussion about this. I think the main thing is that the intent of the lecture is considering the intervals existing in one octave of the major scale. If you look at just the intervals in one octave of the major scale, then a tritone only occurs in one location, between the 4th and 7th degrees of the one octave scale. The actual tritone from the Tonic doesn't exist in the major scale note sequence. – Alphonso Balvenie Jul 4 at 6:48
  • @Alphonso Balvenie- I am more confused by the statement that there are only six tri-tones for the twelve major keys. My studies haven't defined the tri-tone as the interval between the fourth and the seventh. Instead, I learned the tri-tone was the interval consisting of three whole tones (steps) making it possible to apply the tri-tone starting at the tonic. Are my studies incorrect? Did I not get what I paid for? ;) – skinny peacock Jul 4 at 15:08
  • @Alphonso Balvenie- If I understand correctly, the lecture is considering the tri-tone interval to be exactly the same interval after it has been inverted. My studies consider the tritone to be reversed when inverted, therefore resulting in twelve different tri-tones. I'd like to know which way is correct, but it occurs to me I might be overthinking this a bit. – skinny peacock Jul 4 at 15:31
  • @Alphoso Balvenie- It just occurred to me that the confusion I've been having is likely one about definition. It may be that the lecturer is defining a Tri-tone interval as three whole tones, whereas I'm thinking of the tri-tone as the individual notes at each end of the tri-tone interval. From the lecturers definition I come up with 6 tri-tones, and from my own definition I count 12. I've been thinking to hard, time for a break! – skinny peacock Jul 4 at 15:48
  • whatever you do, don't read the tritone inversion link. That's a deep rabbit hole. Yes, same terms, different meanings depending on context. There is the tritone that exists between the perfect 4th and 5th and inverts perfectly to the octave, and a tritone is defined by any jump of three whole tones (steps). The tritone is the dissonance in a Dominant7 chord, and inserting one in Minor scale's dominant chord raises the seventh degree in Harmonic Minor, etc. There is a difference between defining the pitch of the tritone vs the enharmonic naming of the tritones. – Alphonso Balvenie Jul 4 at 18:32
2

Perhaps one way to "see" the explanation is to rearrange the diatonic scale in fifths and then noting the fifths are all perfect except for one...

CDEFGABCD...

Rearrange that in fifths...

CGDAEBFCG...

...you can see that only the B to F is a diminished fifth, a tritone.

Personally, I think the observation should be applied to the diatonic scale rather than the more specific major scale, because then you include the various modes. For example, the Dorian mode contains only one tritone. The same applies for all the modes.

For what it is worth, minor key music has two characterisic tritones: the leading tone to the sub-dominant, and the supertonic to the (lowered) mediant.


EDIT

I didn't see your specific question...

In the left figure, why can't C-F# be another tritone for C maj? In the right, why can't F#-C be another tritone for F# maj?

Diatonically speaking you won't be in the key of C major if you use an F#, and you won't be in F# major if you use a C natural.

Of course you can play those tones and still be in the respective keys, but they will be chromatic. For the purpose of the discussion "in the key of..." means the diatonic tones of the key signature and not chromatic tones.

The major/minor key system is a mix of diatonic and chromatic tones. Chromaticism can take the form of chromatic embellishment or shifting modes/tonics. "Being in a key" can be thought of has applying on different levels global or local. For example, a sonata in C major might contain passage that temporarily shifts into D minor. Globally the sonata is in C major, but the passage is locally in D minor.

You in one sense your are correct. You can have the tritone C F# in C major using chromatic harmony like V43/V V V42 I6.

On the other hand, if we want to discuss only the diatonic tones of the key signature, the tritone C F# is not in C major.

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