Video lesson on a fundamental piece of music theory

ReaGeorgeReaGeorge Posts: 108Member
Here's my latest video lesson on a fundamental piece of music theory. As with a few of my recent lesson videos, this is some theory that I think allot of more casual guitarists maybe aren't aware of, or maybe haven't taken the time to understand properly, but it's vital to understanding scales and chords and I think is therefore a very important/useful bit of theory.    


  • JockoJocko Posts: 6,871Member, Moderator

    Intervals are a bugbear of mine so I have downloaded your video and I will keep for future reference. I am currently reading up on intervals and even after a great deal of exposure still find some of the concepts less than easy to assimilate.

    One question. What makes a Perfect Interval "perfect"? Why is a Perfect fifth more "perfect" than a Major third?

  • Reg SoxReg Sox Posts: 3,121Member

    If someone buys you a third of a gill of whisky it's a major shot.  But if they buy you a  fifth of whisky (a whole bottle) it's perfect.


    I assume that explains it adequately?


    Coat on and leaving..........

  • ReaGeorgeReaGeorge Posts: 108Member
    Originally Posted by Jocko:

    What makes a Perfect Interval "perfect"? Why is a Perfect fifth more "perfect" than a Major third?

    That's kind of an interesting question, I wouldn't say it's particularly important to know from a practical musical theory perspective as long as you just know that Unisons, Fourths, Fifths and Octaves are all perfect.


    It's kind of a mathematical or scientific reason in a sense, I don't completely understand it myself, but as far as I can tell its to do with the fact that their ratios of the difference in frequencies are whole numbers, or something along those lines. This of course is something that comes across musically as having a good sound, hence why we have the circle/cycle of fifths/fourths which is such a common movement in music in general.


    Allot of musical theory can be explained mathematically or scientifically but obviously as a musician it's not really necessary to understand all that.


    Hope that makes some sense image



  • Reg SoxReg Sox Posts: 3,121Member

    It's about intersecting wave lengths and ratios.  A perfect fifth has a 3:2 relationship where the higher note will have exactly three wavelengths compared to exactly two for the lower note.  Other "perfects" have other relationships.  Non "perfect" intervals will cause the characteristic "beating" if the two notes are played together, whereas the perfect intervals won't because the waveforms cross the zero point together.


    Jocko - with your electronic engineering background think overlapping sine waves on an oscilloscope where the zero point crosses are in sync versus where they aren't.


    This also goes back to some of the recent tuning discussions.  A real perfect fifth etc will only relate to an instrument that is perfectly in tune to a single key.  All multi-scale instruments such as pianos and our guitars use tempered tunings so in reality for our use there is no scientific "perfect fifth" or other perfect interval, just it's use as a musical notation convention as tunings are approximate (tempered).


    Break music down into science theory and I can talk all day.  Just a pity I can't read a bloody note of it in it's usual environment


    Cheers, Reg..

  • JockoJocko Posts: 6,871Member, Moderator

    That's great. A bit of science does it for me. Without proof I don't believe it. My wife told me that the lassie in the next block had "perfect" breasts but I didn't believe her until I felt them for myself. That's the sort of guy I am. Science and proof driven.

  • Reg SoxReg Sox Posts: 3,121Member

    A woman with a  fourth or fifth breast, however perfect, is just a bit too weird for my taste Jocko.  I'll settle for a major second and leave it at that.

  • JockoJocko Posts: 6,871Member, Moderator

    The book I am currently reading "Music Theory for Guitarists". by Tom Serb. has answered my question as to what makes a Perfect Interval, "perfect".

    If you invert a Perfect Interval, say C to F, and then get F to C, then the interval is still Perfect (ie. a Perfect 4th becomes a Perfect 5th). However if you invert a Major interval you get a Minor Interval, etc, etc.

    Apart from that gem the book has little to commend it. To top it all I am reading my copy for the third time, and the pages are falling out en masse. Once I have read it through it is going in the recycling.

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