Music Theory Trivia

[C&M Music - Lafayette]

The purpose of this thread is to enthuse the interest in music theory. If you know music theory, all the better. Jump on board for the rest of us. Anyone just learning a tid bit from this thread; if it is successful; like it or not; will be a better player for it as the information at some point will be useful?

That said, I will start with two questions just to get it going. When you answer a question your reward will be to post a trivia question of your own. Here it goes.


1) What differentiates the minor pentatonic scale from the blues scale? What is this difference often refrenced as?


2) What scale contains the note, C flat? Why?

 

[veinbuster]

1) you include the diminished 5th - the not between the 4th and 5th. It gives the scale a nice mournful sound.
2) C flat would really be B, so on a technicality it isn't in any scale - but B is the 7th of Cmaj, and in lots of others.

 

[C&M Music - Lafayette]

Thank you for answering veinbuster.

Right on No#1. Yes adding the flatted fifth to the minor pentatonic gives you the blues scale.

Wrong on No#2 A certain major scale does contain two B notes, which is a tested muics lesson that actually proves the truthful facts to music theory. What scale?

 

[andymue]

Gb major contains Cb

 

[Mikegarveyblues]

Cb Major?

Some instruments use this key don't they? Although most would use B major.

edit: According to Wikipedia the harp has been notated in this key.

 

[C&M Music - Lafayette]

Gb major contains Cb

Correct andymue? The key of G flat major has a b flat and the next note in the scale is the B. The formula theory for the scale pattern identifies the B as a C flat.

 

[C&M Music - Lafayette]

Cb Major?

Some instruments use this key don't they? Although most would use B major.

edit: According to Wikipedia the harp has been notated in this key.

Yes Mike correct also.

 

[rugerpc]

1. Adding the flatted fifth to the minor pentatonic scale gives the blues scale. This note is called "the blue note".

2. There are more than just 2 scales which use Cb. The most common ones are Gb and Cb. But there are actually more, a total of seven.

• Fb where every note is a flat except B which is Bbb (B double flat)
• Bbb with B double flat and E double flat (Bbb, Ebb, Ab, Db Gb, Cb, Fb)
• Ebb with Bbb, Ebb, Abb Db, Gb, Cb, Fb
• Abb with Bbb, Ebb, Abb Dbb, Gb, Cb, Fb
• Dbb with Bbb, Ebb, Abb Dbb, Gbb, Cb, Fb

This is music theory after all. And though the extra 5 scales with Cb are seldom seen - they exist.

Note: the double Bb contrabass clarinet is not voiced in Bbb - it gets its name because it sounds 2 octaves lower than the standard Bb soprano clarinet and is written like this: BBb Contrabass Clarinet.

Confusing isn't it?

 

[andymue]

• Fb where every note is a flat except B which is Bbb (B double flat)
• Bbb with B double flat and E double flat (Bbb, Ebb, Ab, Db Gb, Cb, Fb)
• Ebb with Bbb, Ebb, Abb Db, Gb, Cb, Fb
• Abb with Bbb, Ebb, Abb Dbb, Gb, Cb, Fb
• Dbb with Bbb, Ebb, Abb Dbb, Gbb, Cb, Fb

I once was taught, that every major scale has at most one # or b for every note.
I.e. those scale that require double #/b should be notated with the enharmonic-equivalent to avoid the double #/b
But obviously, in theory, you can just as well build the scales using double #/b.

Ok, to keep the thread going:
What's special about the notes of the three major triads of a major scale?

 

[Saruman]

Ummm... they contain 9 notes, among which al the 7 notes of the scale itself?
In Cmajor, the triads are
I = Cmaj = C/E/G = 1/3/5
IV = Fmaj = F/A/C = 4/6/1
V = Gmaj = G/B/D = 5/7/2

 

[andymue]

^^ correct.
The 3 major triads contain every note of the scale.

 

[Saruman]

OK let me throw in a slightly more challenging question:
A) what is the definition of an octave (I'm looking for a physics answer, not "12 semi-tones")
B) why do we have 12 frets in an octave, instead of, say, 13 or 11?

 

[andymue]

A) frequeny is doubled
B) Because we decided historically that we want to use a 7 note scale with 5 full and 2 half tones?
;-)

 

[Saruman]

A) correct
B) nope.. the 7 note scale is a somewhat arbitrary choice within the 12 semitone octave.You play different scales as well: "blues scale" which is hexatonic, pentatonic scales, which are, umm, pentatonic, and jazz does octatonic.
The reason that so many scales "work" has to do precisely with the fact that we have 12 frets, not 13 or 11.
Hint: an important part of our music theory originated with this bloke some 2500 years ago that walked past a hammering blacksmith.

 

[Saruman]

... long boring answer...

If no one knows, it may be of interest to look up the "pythagorean hammers". Pythagoras found that frequencies that are in certain proportions to each other sound well (consonant) while the rest sounds not so well (dissonant). The proportions that sound well are 1:1, 2:1, 3:2, 4:3, 5:4, 9:8...

If I'd play on a synthesizer two tones in one of these proportions, a musician could label the proportion, or interval, this way:

• 1:1 - unison
• 9:8 - major second
• 5:4 - major third
• 4:3 - perfect fourth
• 3:2 - perfect fifth
• 2:1 - octave

OK this sounds reasonable and is still easily understood, right? But now comes a hard part with logarhythms and roots and squares - let me skip some mathematical work to spare those that don't like that.

Let's fit twelve intervals of logarithmically increasing length in a single octave. Let's also skip ahead a bit and call these intervals "frets". This now means that moving your finger one fret up increases the note's pitch with a factor of 1.05946 (the twelfth root of 2). Moving two frets increase the pitch with factor 1.1125, three frets is 1.1892, .... , 11 frets is 1.88775, and 12 frets is exactly 2.0000.

If we look specifically at the distances of 2, 4, 5, 7, and 12 frets, we find the following pitch factors:
[TABLE="width: 500"]
[TR]
[TD]2[/TD]
[TD]1.122[/TD]
[TD]almost 1.125[/TD]
[TD]= 9:8[/TD]
[TD]major second[/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]1.260[/TD]
[TD]almost 1.250[/TD]
[TD]= 5:4[/TD]
[TD]major third[/TD]
[/TR]
[TR]
[TD]5[/TD]
[TD]1.335[/TD]
[TD]almost 1.333[/TD]
[TD]= 4:3[/TD]
[TD]perfect fourth[/TD]
[/TR]
[TR]
[TD]7[/TD]
[TD]1.498[/TD]
[TD]almost 1.500[/TD]
[TD]= 3:2[/TD]
[TD]perfect fifth[/TD]
[/TR]
[TR]
[TD]12[/TD]
[TD]2.000[/TD]
[TD][/TD]
[TD]= 2.1[/TD]
[TD]octave[/TD]
[/TR]
[/TABLE]
Using 12 frets, the fun part is that "almost" in this little table is good enough for us, since most all people can't hear the difference. Cool! With 12 frets in an octave, we can use all of those ratios, or intervals, when we play the guitar, and our fretboards give us those intervals independent from where we start, both up and down: you can go up or down by 4 frets, and hear a major third (even though it's slightly too high, off by a factor of 1.007937, that's too small to discern).

If you had 13 frets, you'd also have to use 4 frets for a major third, but it'd be slightly too low, off by a factor of 1.009916 - you'd definitely hear that.

If you had 11 frets, you'd again have to use 4 frets for a major third, but it'd be much too low, off by a factor of 1.02933 - you really really wouldn't like that, but the 5th fret is even further away from the major third!

I could bore you some more, but I'd rather hope I've already shown why 12 frets in an octave on our instruments works well, and why ordering a guitar with 11 or 13 frets in an octave might not work as well. Of course, Wikipedia is full of articles on scales, intonations etc. that are much more elaborate, correct, and boring than this not-so-little post...