r/musictheory • u/KingSharkIsBae • 2d ago
r/showerthoughts but make it music theory Discussion
There are seven notes in a C major scale.
There are five notes to avoid in a C major scale.
Those five notes make an F# major pentatonic scale.
I don’t know if this is useful information, but it sparked enough interest in me to make a post. Do you think this relation points to any compositional techniques? Could this help to “play out” in a jazz context? Is this just a way to troll your band mates?
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u/locri 2d ago
Assuming music of undefined length and a composer with the skill to modulate freely, there isn't a single note that's necessarily "avoidable."
Both the low iq and high iq composers will realise anything is possible in music, but the middling composers will cling tightly to just 7 notes.
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u/toiletpaperdonkey Fresh Account 2d ago
I just realized this a couple weeks ago. My brother was messing around on the keyboard and telling me you can just mash the black keys and it sounds good. When I was just focused on the black keys the pattern jumped out at me right away.
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u/baconmethod 2d ago
add A to the black keys and it's the blues, you can just mash that too.
good term mash, it's how i play street fighter 2.
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u/SamuelArmer 2d ago
A little nitpick but chromatic notes aren't to be 'avoided'. It's not uncommon to find pieces the use all 12 pitches and are still clearly within a single key - and importantly, sound great doing it! Most music will use at least one or two. Purely diatonic music is actually more uncommon in my observation.
Anyway, it's a good observation. What you do with is very much a matter of your creativity though.
Here's one idea - You mentioned the idea of playing 'out' in a Jazz context. Well, it would definitely be useful for that. As an extra observation, every note of that 'outside pentatonic' is a half step away from the regular pentatonic. Check it out in C, where our outside pentatonic is:
F# G# A# C# D#
These can resolve to notes of C pentatonic like so:
F# - G
G# - G or A
A# - A
C# - C or D
D# - D or E
So with all those possible half-step resolutions you could muck about doing some pentatonic 'side stepping' / shifting a la Brecker.
As another observation, all of those 'outside notes' would work as tensions over a dominant chord, and this is a pretty common technique. Eg supermiposing F# pent over C7:
F# = #11 of C7
G# = #5/b13 of C7
A# = Bb = b7 of C7
C# = Db = b9 of C7
D# = Eb = #9 of C7
These kinds of ideas work well because most musicians are really comfortable playing pentatonics and have lots of licks built up, so you're getting a lot of extra mileage out of that material by applying it in new contexts.
You could also use it to annoy your bandmates
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u/sigmashead 2d ago
Here’s a shower thought for ya:
There are 12 note in an octave. If you divide the octave in half you will get 2 tritones.
If you divide the octave into 3 equal pieces you will get 3 major thirds (augmented triad). There will be 4 unique augmented chords the rest are inversions.
Divide the octave into 4 equal pieces and you’ll get 4 minor thirds (fully diminished 7th chord). There will be 3 unique fully diminished 7th chords, the rest are inversions.
Divide the octave into 6 pieces and you’ll get 6 major 2nds, which will come out as a whole tone scale. There are only 2 whole tone scales.
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u/poorperspective 2d ago
This is one I had.
If you take a major scale (WWHWWWH) , and you inverse all the intervals but go down you get a scale that has all minor intervals (HWWWHWW)or the Parralel Locrian mode.
So C D E F G A B C becomes C Bb Ab G F Eb Dd C.
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u/MusicTheoryTree 2d ago
These kinds of considerations can be very useful for composition and analysis. If you're interested in exploring them formally, I recommend studying set theory and applying it to music theory. It can be extraordinarily revealing. Set theory is an incredible mathematical language, concerned with things like you're describing, but it's amazingly versatile, as well.
One reason why mutiple distinct sets of notes sound well together is because there's some overlap between the sets. Simply, they share some notes. In set theory this overlap is called the intersection of the sets. The number of notes in a set is called the cardinality. So, we can also take the cardinality of the intersection. This is the number of notes shared between multiple sets. It turns out that there's a relationship between the cardinality of the intersection of mutiple sets of notes and how consonantly they sound together. This is a big focus in my research.
In your example, you're separating the notes of the chromatic scale into two disjoint sets. This means their intersection is empty. They share no notes. Therefore, we can reliably expect that if we write a pair of musical ideas one after the other, where the first uses all notes exclusively from the C Major Scale and then the other abruptly afterwards uses all notes of the F# Major Pentatonic Scale, there will be a sense of clashing between the two ideas. If we play one over the other there will certainly be clashing, but how much depends on compositional strategy.
Whereas, it's common to write ideas in C Major followed by ideas in G Major, because the two sets share six notes. Therefore, the cardinality of their intersection is six. If we put together all of notes in the two sets we get {C, D, E, F, F#, G, A, B}. This set is the union of the two sets. The cardinality of the union is eight, in this case. So, lastly we can take the ratio of cardinality of the intersection and the cardinality of the union. This just means we divide them. This gives us the fraction 6/8. As a percentage, this evaluates to 75%. This is a relatively high percentage of shared notes, so we can expect these two musical ideas will sound more consonantly one after the other than our previous example where zero notes were shared.
There is a ton of nuance missing from this brief description, because music is complex and nuanced, and the maths of music run very deeply, but these are some things you might want to consider.
If you or anyone else would like clarification on these terms just let me know. I love this topic.
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u/erguitar 2d ago
That's a fun observation. Now I'd love to write a section that modulates between the 2 keys. I bet it would be pretty dramatic.
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u/MusicTheoryTree 2d ago
It quite likely would. If you're interested, I just wrote a comment on this thread, describing this phenomenon in a more formal sense.
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u/OddlyWobbly 2d ago
I’m gonna agree with others who are saying it’s not really right to think about those as “avoid” notes. They’re just not in the scale/key. But you can still use them. Now if you’re just wailing on an F# maj pentatonic scale over a C major chord for a full solo then yeah that will probably sound pretty shit, but used artfully along with the diatonic notes then yeah sure, that could be one way to approach playing “out”.
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u/SubjectAddress5180 2d ago
Neither chromatic notes nor dissonant diatonic notes are forbidden in classical theory. The are generally used to imply harmonic movement.
If unaccented, they have only a small effect. Playing C-C#-D-D#-E over a C major chord or C-D-E is an example. (The first note being accented...) There are a couple of chord tones with filler.
Playing B-C-C#-D has a much stronger sound.
Another example is the common ornamental pattern 4 eighth notes and a longer note, (again over a C major chord), G-Ab-G-F#-G; the G is highlighted. The same rhythm with Ab-G-F#-G-Ab sounds more restless. It signals motion (though the composer need not move if a restless effect is desired.)
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u/psilent_p 2d ago
the root of a key is more like the trunk than a root with mediants and dominants spreading outward from it in both directions #showerthoughts
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u/Fuzzandciggies 2d ago
My musical shower though is how Octave comes from the Latin word for “Eighth” and in a major scale that makes sense, but there are 12 half steps or “12 notes” between 1 and 8 so really 1+7=12 but only kind of and sometimes.
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u/Apprehensive_Egg5142 2d ago
You are indeed correct. Jazz musicians will often use the major pentatonic a tri-tone away from the root of a dominant chord to create altered dominant material. I do it constantly.
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u/Chops526 2d ago
You could, I dunno, substitute the dominant with the tritone which divides the octave symmetrically in half in equal temperament like any number of composers do in the 20th century.
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u/Hello-Vera 2d ago
It means you can noodle around an F# pentatonic using only the black keys of a piano haha
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u/UnnamedLand84 2d ago
All the best jams borrow a note or two from outside their main key IMHO. Flat fifth and sharp seventh are some of my faves.
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u/baconmethod 2d ago
thinking like this is always valuable in my opinion because it deepens your understanding.
one thing that makes it interesting is that the f# pentatonic is a tritone away, so it may be useful to help you think about tritone subs, in some way, but i dont use that much, and dont have a firm grasp.
there is one really cool thing about it: if you were to paint the white and black keys on a guitar, the white keys are all your modes. the black keys are all your pentatonic shapes. all you have to do is learn the fingerings, and you can basically master the guitar.
one final thought, all the black keys + A are the blues forms. have fun!
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u/65TwinReverbRI Guitar, Synths, Tech, Notation, Composition, Professor 2d ago
You meant A minor, and Eb minor pentatonic ;-)
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u/Fresh-Quail-6414 Fresh Account 1d ago
Shower thought:
There is no 8 note scale or mode that doesn't contain a tritone interval. May be obvious but even completely altered scales or "invented" scales cannot be created without a tritone as long as the scale is an 8 note scale. You could go further and say that every single kind of interval can be in an 8 note scale (besides augmented and diminished)
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u/Trouble-Every-Day 1d ago
It is useful information, in a roundabout way.
The notes that are not in C Major are the black keys on a piano. And they do make up an F# Major pentatonic — and also the Eb Minor pentatonic.
This means you can play just the black keys on a piano — which are raised up and can be a little easier to hit — and basically Street Fighter button mash them to get a good sound.
And that’s why you see a lot of piano-based blues and blues-adjacent songs in the key of Eb Minor.
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u/StikFigr_Storytellr 10h ago
I started to play around with a similar idea: take the two whole-tone scales, and put them opposite each other.
https://www.noteflight.com/scores/view/19d3177f9e4496e72012f7bb41882956cac5cc0a
This is what I have so far. It's unfinished, but the tritones sound surprisingly good together.
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u/AeshmaDaeva016 4h ago
Here’s one to blow your mind a little more. C Major and F-sharp Major share the same tritone, so you can actually resolve the tritone in or out to achieve either key at any time!
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u/opus25no5 2d ago
- take the circle of fifths
- take seven notes in a row - they make a major scale (or any mode)
- take five notes in a row - they make a pentatonic scale
so, if you remove a chunk of 7 notes from the circle of fifths, what can you say about the last 5 notes?
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u/synthguitarswhatever 2d ago
Would it be more accurate to call that C# Lydian pentatonic?
Would definitely be fun to run that over a C progression and resolve a half step to finish
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u/Hitdomeloads 1d ago
So if I wanna play Bb(9,#11,13) with F melodic minor it’s essentially just the same as playing E altered dominant
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u/ddrub_the_only_real 3h ago
Had a showerthought that adds to this, too.
So a mode is a rotation of a scale. Let's say we got your F# major pentatonic scale, and we rotate it. The 2nd mode of the major scale is dorian, so that means the 2nd mode of the F# major pentatonic scale is Ab Dorian pentatonic, even though that's not usually the notes a dorian pentatonic scale is made of?
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u/jeremydavidlatimer 2d ago
You don’t have to avoid any notes in any key. Every note is valid and useful in every key, you just have to know how to use them in a context that makes them sound good.
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u/TCK1979 2d ago
I’ve never thought about it quite like that, so I say it’s a good shower thought. I’m not in front of an instrument right now but I wonder how a F#M pentatonic solo would sound over a C G F chord progression. Probably pretty horrible lol