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Topic: Music Theory
From the Music Questions forum.

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AuthorTopic:   Music Theory
Anonymous
Anonymous Poster

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posted: 5/26/2006 at 8:42:11 AM ET
Can any help me figure out the difference between a minor interval and a diminshed iterval? I can't figure out why an interval of c to d flat is a minor 2nd and yet an interval of C to F flat is a Diminshed 4th but not a minor 4th. I am studing as a senior citzen music theory to help me learn to play the keyboard.
Thanks JFG.

aramispxxvi
Registered User

From:
Asheville, NC

Registered:
5/15/2006
posted: 5/29/2006 at 9:51:12 AM ET
JFG,

If my Music Theory memory is correct and if not anyone can correct me if I am wrong you're dealing with the number of semi-tones - which are tones between two notes that make up an interval. For example, ascending you may have C, C#, C dbl #, D, D#, D double #, and so forth. Descending you may have F, F flat, F double flat, E, E flat, E double flat, etc ... This may sound confusing but if you take your time with it and realize that enharmonics (tones with different names that sound the same depending on the key you are using) are the "key" here (no pun intended), this will get easier to understand. For example, in the Circle of fifths you see the key of G which only has one sharp - F#. However that same tone is found in the key of G flat and is in fact the very same note although now the name is G flat. I hope that this helps.

"Be Not Afraid" JPII

trumpetrousers
Registered User

Registered:
5/30/2006
posted: 6/8/2006 at 4:53:46 PM ET
aramispxxvi is basically correct, the difference between minor and diminished has to do with the number of half-steps between notes. But I have an easier way to remember what's what:

Seconds, Thirds, Sixths, and Sevenths are called minor when they are lowered by a half-step from the major key.

Only Fourths and Fifths are called diminished when lowered by a half-step.

In other words, Major intervals (2nd, 3rd, 6th, 7th) can become minor, while Perfect
intervals (4th, 5th) become diminished.

What's the reasoning behind this? It comes partly from the fact that harmonically the Fourth and Fifth scale degrees are very important and are used most often in creating cadences. You'll notice that the Fourth and Fifth do not change from Major to minor:

C Maj: C-D-E-F-G-A-B-C

c min: C-D-Eb-F-G-Ab-Bb-C

When lowering the Fourth and Fifth scale degrees theoriticians probably wanted to distinguish these two intervals from the others.

To me, the reasonong isn't all that important, it's just easier to memorize which intervals are which.

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