Double Bass Intervals

[Andy Mopley]

Hi all

I get that the number of semitones apart determines the name of an interval. For example C to Eb, 3 semitones part - minor 3rd. If it was part of a chord, it would also be a minor or diminished chord.

What I don't get is why C to Ab (or G#) is a minor 6th or C to A# also a minor 7th - what is that is "minor" about the interval, apart from the semitones apart??

Regards to all

 

[The Biz]

everything is derived from the major scale...

 

[Mushroo]

C to A is called a "major 6th" because A is the 6th note of the C Major scale.
C to Ab is called a "minor 6th" because it is a half step smaller than a major 6th.

C to B is called a "major 7th" because B is the 7th note of the C Major scale.
C to Bb is called a "minor 7th" because it is a half step smaller than a major 7th.

 

[SAlcott]

I wondered about this terminology in my first theory class in 12th grade; after a few minutes, I realized that it's just a way of describing something intangible with words, learned the words, and that was that.

 

[wathaet]

In other languages equivalents of large and small sixth etc is used.
Major and minor is really just the same meaning.

 

[neilG]

Hi all
What I don't get is why C to Ab (or G#) is a minor 6th or C to A# also a minor 7th
Regards to all

C to G# is not a minor sixth, it's an augmented fifth. C to A# is an augmented sixth. That's an important distinction when you're talking about harmony.

 

[dreamadream99]

What I don't get is why C to Ab (or G#) is a minor 6th or C to A# also a minor 7th

You’ve gotten the right answer already —minor, in this case simply means a semitone lower than the major interval. But now I’m really going to throw you for a loop:

In discussing intervals, an Ab is not the same thing as a G#. Any C to any A is a sixth of some kind; any C to any G is a fifth of some kind. So, C to Ab is a minor 6th, but C to G# is an augmented 5th. By the same token, C to A# can’t be a seventh of any sort. It is an augmented 6th.

 

[SteveCS]

Andy, ask Chris Fitzgerald... he's been teaching jazz theory for 20+ years.

...but does not have the monopoly!

@Andy Mopley

The interval class is defined by the letter names included in the interval as derived from the parent scale. So, as noted above, C to G is always a type of 5th. Sticking with 4ths and 5ths for a moment - the 'quality' can be Perfect, Diminished (narrowed by 1 semitone) or Augmented (widened by 1 semitone). A perfect 5th is, as you noted, 7 semitones. So a diminished 5th (also referred to as a 'flat5' in jazz circles) is 6 semitones. A Perfect 4th is 5 semitones, so an Augmented 4th (#4) is 6 semitones, just like a dim5. The difference is in the letter name.
Take C Lydian scale: C D E F# G...
Now C Locrian: C Db Eb F Gb...
F# and Gb are enharmonically equivalent, ie 6 semitones, but one is an augmented 4th and the other a diminished 5th.

Unisons and octaves can also be diminished, perfect or augmented.

The other intervals (2nd, 3rd, 6th and 7th) can be diminished, minor, major or augmented, but never Perfect. The way to determine the class and quality is the same.

Edit. For clarity, just as those intervals that may be Major or Minor may never be Perfect, Perfect intervals may never be Major or Minor, but all intervals can be diminished or augmented.

 

[neilG]

Intervals can also be double diminished or double augmented.