Flatted 5th not minor 5th

Discussion in 'General Instruction [BG]' started by The Artist, Dec 27, 2007.

  1. Can anyone here tell me why in scales, if you flat the 5th note it is refered to as a flatted fith and not a major fith?
    Just wondered
  2. 73jbass

    73jbass Supporting Member

    Apr 17, 2004
    Because flatting the 5th doesn't make it a minor scale. The 3rd and 7th are what determines the maj/min if I remember correctly. Anybody care to verify?
  3. JimK


    Dec 12, 1999
    I know you meant "minor"...

    The simple answer-
    Pefect Intervals (4ths & 5ths), when flatted, become diminished (not minor).
    It's theoretical.
  4. NJL


    Apr 12, 2002
    San Antonio
    call it a diminished 5th, cause not all lowered 5ths turn into a "flat".
  5. NJL


    Apr 12, 2002
    San Antonio
    +1, you beat me to it
  6. HaVIC5


    Aug 22, 2003
    Brooklyn, NYC
    Perfect intervals are perfect because if you invert them they yield another perfect interval. An inverted perfect fifth is a perfect fourth, an inverted perfect octave is another perfect octave, etc. All other intervals are considered imperfect because when they are inverted, they yield an interval of the opposite value. For example, when you invert a minor 3rd you get a major sixth. Invert a major 2nd and you get a minor 7th. The terms major and minor in this case simply refer to one side of the inversion, which is why you wouldn't have a "minor" fifth - its a perfect interval.

    When you ALTER these degrees, you get diminished/augmented intervals. So the perfect 5th altered down a half step would be a diminished fifth, which is enharmonic to the augmented 4th (the perfect fourth raised up a half step). You can do this to imperfect intervals as well. For example, in a fully diminished 7th chord, you will have an interval of a diminished 7th, which is minor 7th which has been altered by flattening it a half step (this is enharmonic to a major 6). The other common altered imperfect interval is the augmented 2nd, or #9, which often occurs on dominant 7th chords.
  7. Thanks, that is the answer I was looking for.
    Although I do not yet fully grasp it, I'm getting there ;)
  8. Because there isn't an interval that falls between a fourth and a fifth. When you look at the scale in terms of frequency ratios (and assume it's justly tuned rather than tempered), the fifth is 3/2 the frequency of the root. E.g., a fifth above 200 Hz = 3/2 * 200 Hz = 300 Hz. A fourth is 4/3, a major third is 5/4, a minor third is 6/5.

    Simply incrementing the numerator and denominator together will give you the notes in this part of the major scale. But in this sequence of simple intervals there are no notes between the fourth and fifth. To put a note there you must break the sequence and add an interval more complex than either the fourth or the fifth. That note will not sound like a variation on either the fourth or the fifth. Major/minor thirds, on the other hand, are close neighbors in the sequence and do sound like a variation on the same sound.