Okay...what the heck is an overtone???

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Young Angus, Feb 15, 2006.


  1. Young Angus

    Young Angus Member

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    Now most of you will probably think "bloody guy doesnt even know what an overtone is and he owns a komet!" ... and yeah i dont know what an overtone is, but i know a Komet sounds awesome and thats enough for me! But its meant to have some nice overtones...so please in nice easy to understand terms...what is an overtone?
     
  2. AaeCee

    AaeCee Member

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    Maybe different things to different blokes, but here's my take. I notice 'overtones' most on LPs and the like. You hit a note, and hear that pitch along with a ring or bloom on another level, usually at a much higher register. It can be like a sparkle or edge or bite to the note, again, in tune with the note, but with a different dynamic than the pure note alone. Kinda hard to describe...like McGlaughlin said 'words can't describe music', but I know them when I hear them. AC
     
  3. Bryan T

    Bryan T Guitar Owner Silver Supporting Member

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  4. 1-Take-Wonder

    1-Take-Wonder Member

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    From an audio geek website...

    Harmonics: Also called overtones, these are vibrations at frequencies that are multiples of the fundamental. Harmonics extend without limit beyond the audible range. They are characterized as even-order and odd-order harmonics. A second-order harmonic is two times the frequency of the fundamental; a third order is three times the fundamental; a fourth order is four times the fundamental; and so forth. Each even-order harmonic: second, fourth, sixth, etc.-is one octave or multiples of one octave higher than the fundamental; these even-order overtones are therefore musically related to the fundamental. Odd-order harmonics, on the other hand: third, fifth, seventh, and up-create a series of notes that are not related to any octave overtones and therefore may have an unpleasant sound. Audio systems that emphasize odd-order harmonics tend to have a harsh, hard quality.

    ...same applies to guitar amps pretty much. Certain harmonics can be emphasized based on the circuit design.
     
  5. brad347

    brad347 Member

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    The overtone series is the order of harmonics, or partials, that ring along with a note that you play, called the "fundamental."

    Try this: Without holding down the pedal, go to a piano and depress middle "c" but don't strike the note so that it sounds... just gently put the key down so as to remove the damper from that string. Then strike and remove the C one octave lower... you will still hear that middle "c" ringing, vibrating sympathetically because of the first partial of the note one octave below!

    There is a fixed overtone series, if memory serves, it goes something like this:

    partial 1: one octave above the fundamental
    partial 2: 8ve+ perfect fifth above...
    partial 3: 2 8ves above
    Partial 4: 2 8ves + major 3rd above

    on and on and on... eventually you get a slightly sharp flatted 7th degree, and a slightly flat raised 4th degree.

    Claude Debussy and other composers used to make chords based on the overtone series. The most popular "overtone chord" is the dominant 7th raised 4th, or "lydian dominant." Listen to a lot of Debussy's music (and a lot of jazz pianists) to hear this chord.
     
  6. brad347

    brad347 Member

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    PS this is the same principle that harmonics on the guitar work from. Each time you divide the length of the string (between the nut and bridge) in an even fraction, you get what's called a "node." You can juggle partials by doing stuff with these nodes. If you lightly touch the string at the node, you remove all frequencies except the node's partial frequency. Concurrently, if you pick the string right at the node, you REMOVE the node frequency and let all others ring! (not too many people know that one!) If you fret a note, then of course the distance between the "nut" (now the fret your finger is behind) and the bridge changes, throwing the fractions all different... so whether you know it or not, distortion pedal or not, your right hand is juggling partials all of the time! The distortion pedal just excites this.

    Backing up a bit for some examples, here are some common nodes:

    The 12th fret harmonic divides the string exactly in half, so you get one 8ve above the string's fundamental pitch.

    If you divide the string exactly into thirds, you get nodes at the 7th and 19th frets. These produce a node frequency of an octave and a fifth above.

    If you divide the string exactly into 4ths, you get nodes at the 5th, 12th, and 24th frets. Since the 12th was used by a lower partial already, it defaults to that. The other two produce a node frequency of two octaves up from the fundamental.

    To get the major third, divide the string into five parts (4th fret, 9th fret, 16th fret, and somewhere between neck and middle pickups on a strat are the nodes). This one requires a little more finesse to get but is definitely very strong with distortion especially.

    The first node for the dominant 7th is about halfway between the 2nd and third frets, i'm not sure at the moment how many parts you're dividing the string into, I don't remember and I don't feel like doing the math.

    The same principles apply to artificial harmonics.

    WHEW that was long. Hope I didn't just muddy the waters further. Good luck.
     

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