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Topic: Where are my 17th fret harmonics? |
Frank Freniere
From:
The First Coast
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Posted 7 Jan 2022 10:21 am |
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Why is it so difficult to get harmonics on open strings at the 17th fret?
I admit my technique isn't the greatest but 5,7,12,19,24: no problem.
At fret 17 I can get 3 strings to sound weakly (8,6 and 5) but these may be just be overtones and not a true chime. Also, near as I can tell 8 gives me a true octave but 6 and 5 are giving me thirds (C and Eb, respectively). Why wouldn't these notes line up with those on fret 5? Is it operator error or is there a physics or acoustics explanation for this phenomenon? |
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John Larson
From:
Pennsyltucky, USA
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Posted 7 Jan 2022 11:04 am
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What does you pickup spacing look like? If the pickup poles are directly under the node of a given harmonic it will not sound.
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- Psalm 33:1-5 |
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Frank Freniere
From:
The First Coast
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Posted 7 Jan 2022 11:32 am
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Hey John -
Thanks for the quick response. So does my doctored photo below illustrate what’s going on? IOW I’ll never get the 4th harmonic at the 17th fret unless I move my pickup ?
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Dave Mudgett
From:
Central Pennsylvania and Gallatin, Tennessee
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Posted 7 Jan 2022 1:16 pm
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Are you sure you're not confusing the 17th with the 19th fret harmonic? The 19th fret harmonic is the relatively strong 3rd harmonic, which is the same as the harmonic at fret 7. Even some online sources get this confused - e.g., https://www.guitarmasterclass.net/wiki/index.php/Harmonics - note that they state that the 17th fret splits the string in thirds, but that is the 19th fret as Figure 3 clearly shows.
The 17th fret harmonic is also different than the 4th harmonic at fret 5, which also occurs at fret 24 (1/4 the scale length from the nut and bridge, respectively). The 2nd (octave), 3rd (frets 7 and 19), and 4th (frets 5 and 24) are the strong-sounding harmonics.
The reason you're having trouble with the 17th fret harmonic is that it is generally weak - significantly weaker than the relatively strong harmonics at frets 5, 7, 12, 19, and 24. The 17th fret is approximately at 3/8 of the scale length from the string termination at the bridge (5/8 of the scale length from the nut). This produces the 8th harmonic, or 3 octaves above the open string pitch. Strength of the harmonic series generally decreases as you move up in frequency. By the time you get up to the 8th harmonic and beyond, they're significantly weaker and harder to sound.
A strong pickup magnet near the strings can indeed weaken a note somewhat or even cause a change in the natural vibrating frequency. But I've never seen a pickup magnet actually cancel a note. I just tried a bunch of guitars, steel and standard, and they all sound a relatively weak 3-octave 8th harmonic at around the 17th fret and a bit above the 8th fret - 3/8 of the scale length from the bridge and nut, respectively. These harmonics technically also occur between the 2nd and 3rd fret and near the bridge - 1/8 of the scale length from nut and bridge, respectively - but are harder to sound.
More on stringed instrument harmonics here - https://en.wikipedia.org/wiki/String_harmonic |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 7 Jan 2022 2:15 pm
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You can pick a harmonic at different places on the same fret. You can pick the string on either side of the node, or "touch-point", and sometimes one will be more active (work better) than the other.
Personally, I've always gotten a better sound by picking the harmonic between the touch-point and the nut, instead of between the touch-point andthe changer. But different players and different guitars can produce different results.  |
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Dave Mudgett
From:
Central Pennsylvania and Gallatin, Tennessee
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Posted 7 Jan 2022 3:12 pm
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Because the frets are spaced for equal temperament, some harmonic nodes are not exactly at the fret. If you read that wikipedia article fully, you will see the formula for the fret number of various nodes:
F = log(b, m / (m-n)) where
b = 2^(1/12) (12th root of 2) ~ 1.059463094
m is the harmonic mode number
n is the node number (numbered from the nut)
So the 4 odd nodes of the 3-octave 8th harmonic mode are at frets
Node 1: log(b,8/(8-1)) ~ 2.311740935
Node 3: log(b,8/(8-3)) ~ 8.136862861
Node 5: log(b,8/(8-5)) ~ 16.98044999
Node 7: log(b,8/(8-7)) = 36
Technically, there are also nodes of the 8th harmonic present at even values, but these harmonics are generally drowned out by the much stronger 2-octave 4th harmonic at nodes 2 and 6 (frets 5 and 19), and 1-octave 2nd harmonic at node 4 (fret 12). |
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Frank Freniere
From:
The First Coast
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Posted 8 Jan 2022 4:46 am
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Thanks to all for the responses.
I was finally able to coax out very faint harmonics on open strings 8, 6 & 5 at fret 17 by using the tip of my fingernail - won't be using them any time soon. |
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Dale Rivard
From:
Ontario, Canada
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Posted 8 Jan 2022 7:30 am
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| I find it sometimes helps to alter the position of the right hand(where you strike the string(s)) when playing left hand harmonics. |
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