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Can somone explain why you can only use harmonics on certain frets?

Discussion in 'General Instruction [BG]' started by brink22, Nov 26, 2003.


  1. brink22

    brink22

    Oct 5, 2003
    I've noticed on a bass, like a guitar, you can only use harmonics on the 5, 12, 19, etc frets. I dont get how this works. Why do none of the other fret harmonics ring out?
     
  2. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    It is all about physics. Harmonics are the process of creating a standing wave on the string. This will only occur when when the partially fretted note is at a position that is an integer division of the string. In fact, it really only works for smaller integers. The 12th fret is at half the length of the string. The 5th fret is at 1/4th the length of the string. You can figure out the rest.
     
  3. xyllion's explanation is realy good. :) I may or may not be able to give a spin on the explanation that will help you understand....

    Here's another way to think of it:

    When you set a harmonic, you are causing the string to vibrate fundamentally in a sine wave. When you pluck the open string, the sine wave's nodes are at the nut and bridge (max amplitude is at the 12th fret). When you sound the 12'th fret harmonic, the sine wave's nodes are at the nut, 12th fret, and the bridge (max amplitudes are 1/2 way between the nut and 12th fret, and 1/2 way between 12th fret and bridge) and so on.

    In order to set a harmonic of a string, you must set a node which is divisible by the length of the string, however the division cannot be too high of a number... if the division is some number higher than, say 8 - (by which you are trying to set the string into harmonic vibration with 8 or more nodes) you won't hear much... this is mostly due to the mass and rigidity of a bass gauge string. Guitar strings (less mass, less rigidity) can reach a greater number of nodes. But we're bass players so we don't much care about that. :)
     
  4. Bruce Lindfield

    Bruce Lindfield Unprofessional TalkBass Contributor Gold Supporting Member

    You can play artificial harmonics at every fret ;) - but it's important to remember that it's not frets we're talking about, but subdivision of string length, as several harmonics don't appear exactly over the fret line - like those between the 3rd and 4th frets.

    There are a lot more harmonics than you think - but you have to be accurate about placing them or they don't really sound.
     
  5. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    Try working your way down from above the fifth fret towards the nut - you'll find some harmonic nodes there that don't clearly sit above any one fret. The frets are a useful visual reference point but they've got nothing to do with the note produced...

    Wulf
     
  6. Bruce Lindfield

    Bruce Lindfield Unprofessional TalkBass Contributor Gold Supporting Member

    Isn't that what I said!! :rolleyes:

    Never mind....I'll live with it! ;)
     
  7. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    It's almost what you said - although 'work down from the fifth fret' will yield more results than just searching between the 3rd and 4th frets.

    Look on it as another facet ;)

    Wulf
     
  8. steve_man

    steve_man

    May 15, 2002
    ya there is a lot more harmonics that are available! - try mixing them up with real notes and creating chords (this sounds really nice)

    I recently just bought a new chorous pedal and for some reason (maybe you guys could explain?) I have to be a little more precise when doing artificial harmonics because it's picking out the detail of an say an artificial 4th fret or 6th fret harmonic when I move ever so slightly from the 5th fret artificial harmonic.
     
  9. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    steve_man,

    Do you mean 'artificial harmonics' or 'natural harmonics'. FX like chorus will bring out nuances of the sound but I'm not quite clear on the situation you're describing.

    Wulf
     
  10. Bruce Lindfield

    Bruce Lindfield Unprofessional TalkBass Contributor Gold Supporting Member

    Well as everybody has been saying - harmonics don't relate to frets, but rather to subdivision of string length - the more accurate you are in relation to this, then the louder the harmonic will sound - no matter what effect (or not) you are using.

    So - if you subdivide the working string length exactly by a half, (regardless of where the frets are) you will get a clear octave - if you are slightly out, (but possibly over a fret), it will be "choked".

    Think about distance between nodes and not frets!!
     
  11. JimK

    JimK

    Dec 12, 1999
    "Portrait Of Tracy" is the classic example of this.
    It can be deceiving sometimes, too...the fingers may be moving up the neck while the harmonics sound as though they're descending.
     
  12. steve_man

    steve_man

    May 15, 2002
    I am doing artificial harmonics.

    And Bruce I know about the octave thing.
    But I'm not choking the harmonic. I'm getting
    13th fret harmonics or a 6th fret harmonics with the chorus on instead.

    However when the chorus is off I can't get this.


    I'm also able to get a harmonic that's an entire octave higher than a normal 12 fret artificial harmonic (in the same position) by having the chorus on and placing my thumb a little more off of the fret board.
     
  13. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    I still can't figure out what you're doing. Referring to frets makes even less sense when referring to artificial harmonics than when talking about natural harmonics, when the positions of the harmonics available depend on which note you are fretting to begin with.

    Take this scheme instead:

    1st harmonic: one octave above the original note

    2nd harmonic: one octave + perfect fifth above original note

    3rd harmonic: two octaves above original note

    4th harmonic: two octaves + major third above original note

    There are more, but this should be enough for now.

    With an open string you can play them above the 12th, 7th, 5th and 4th frets respectively. If you experiment, you also find some of them occur more than once - so the 4th harmonic can also be sounded above the 9th fret.

    Above an open D string, for example, the notes you're listening for are D (1), A(2), D(3) and F#(4). Play artificial harmonics from a fretted Bb and you get Bb(1), F(2), Bb(3) and D(4).

    Can you use this nomenclature to describe what you're trying to achieve (which harmonic you're trying to sound) and what note you actually hear?

    Wulf
     
  14. steve_man

    steve_man

    May 15, 2002
    for 13th fret harmonics "artificial harmonics" I mean I'm using my thumb to touch the 13th fret above the fret I'm pressing on the fret board.

    from my experience every note has a natural harmonic not just the 7th, 5th and so on.

    try on plucking really hard on the E string while almost muting G you may notice a natural harmonic.

    this is so for any fret on your bass. But usually because of your setup and touch the harmonic is lost and you hear the mute sound. However with the right setup and right touch you can bring out the sound of harmonics outside of your regular 5th, 7th, 12th

    and I found that this chorus pedal I have brings them out better. So much in fact that when playing 12th fret artificial harmonics I found a new touch and was able to play an entire octave higher than a normal artificial 12th fret harmonic
    (from the regular artificial harmonic 12th fret position)
    ;)

    any clearer?
     
  15. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    Not a huge amount - 13 frets higher than the fretted note just gives me a muted note, although I can get a hint of the '12th fret' harmonic (or first harmonic, by my system above). My guess would be that the chorus pedal accentuates some of the higher frequencies and so you're getting some results despite what sounds like an imprecise technique.

    Here's an experiment - while playing an open string, work up and down it slowly, lightly touching the string. You'll get a whole range of different sounds - including really clear, bell like ones (when you're on a harmonic node) and the near misses when you're in the right ball park.

    Stick on an effect or two to bring out some of the higher frequencies (like chorus and distortion), play it a bit faster and, voila, instant 'heavy metal' guitar hero territory ;)

    Wulf
     
  16. steve_man

    steve_man

    May 15, 2002
    ________________________________________________
    you're getting some results despite what sounds like an imprecise technique.

    _________________________________________________

    actually it started out by playing mutes really fast and I noticed that I was getting what you described as "a muted note with a hint of the harmonic". I played it a little faster with a lighter touch and voila.

    you might get a better result by playing fast mutes normally on the 1st 3 frets on what ever string. This will give you a natural harmonic outside of your normal 4th, 5th, 7th, 12th, etc. natural harmonic
     
  17. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    What notes are you producing with your harmonics? There are several nearer the nut than the third fret on an open string but they get progressively less useful (more noise, less distinct note). Just below the third fret (two octaves plus minor 7th) is the highest one I find useable without extreme EQ settings and even that is not particularly strong.

    Remember that a harmonic is formed by damping some of the lower frequences that make up the timbre of the note - when you play the A string (55Hz) you're hearing that pitch blended with 110Hz, 165Hz, 220Hz, etc. When you hit the harmonic above the seventh fret, you're hearing 165Hz, 220Hz, etc - distinguishable as an octave and a fifth above the original note but lacking the volume contributed by those lower frequency portions.

    The higher the harmonic, the more precisely you need to hit it, otherwise you'll get a semi muted harmonic or a full muted note (depending on how near you are to a node point and how sensitive it is).

    Incidently, this is why clean muting requires more than just one finger lightly touching the string, to stop the vibration rather than filtering it. That's not to say your technique isn't a useful way to produce some musical effects but I'm still not convinced you've discovered new harmonic :)

    Wulf
     
  18. steve_man

    steve_man

    May 15, 2002
    ok I just something in one of your last posts that makes some sence.

    ________________________________________________

    Here's an experiment - while playing an open string, work up and down it slowly, lightly touching the string. You'll get a whole range of different sounds - including really clear, bell like ones (when you're on a harmonic node) and the near misses when you're in the right ball park.

    ________________________________________________


    I was getting the term harmonic confused with the bell like tones. What would these notes be called?

    Also I can get a bell like tone out of the 12th fret artificial harmonic. I think this is the result of what you'd call "imprecise technique".

    ahh! I think I've got it. I was wondering why I could get more than one tone (the harmonic and the bell like sound) from the same fret position (harmonically speaking).:D

    Would this be caused by the chorus pedal?
     
  19. wulf

    wulf

    Apr 11, 2002
    Oxford, UK
    I think your "bell-like" is the opposite of my "bell-like". What I mean is the quality of sound you get above the 12th, 7th and 5th frets (the first three notes of the harmonic series, which are the clearest) and at various other points up and down the string. I think our misunderstanding comes from the fact that we're using the same terminology to talk about different things.

    If you took out a tape measure, you'd find that there was a distinct pattern to where the harmonics sound clearest.

    For example, the first harmonic is above the 12th fret, which is the midway point between the nut and the bridge and sounds an octave above the open string. Without a bass to hand, I'm still pretty confident that the third harmonic, two octaves above the open string and found above the fifth fret, is a quarter of the way along the string. You'd also find the same harmonic note if you touched the string a quarter of the way in from the bridge instead of from the nut.

    Wulf
     
  20. steve_man

    steve_man

    May 15, 2002
    how the concept works.

    I still think you answered it before.
    Because if I go to play a harmonic I don't get a dead thud. I get a note that rings at a higher pitch. I thought kinda like a bell. :D

    Anyways I can make an cool noise. I'm leave'n her there.

    cheers!:cool: