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Assumption: The 12th fret is meant to be the middle point of a guitar or bass string.

So I expected the harmonics to repeat after the 12th fret. ie 3rd 5th 7th harmonics and so on would be like 15th, 17th, 19th etc.

And they mostly do match up.

But I was surprised to realise I can get much better harmonics from the 16th fret than the 15th. Same with the 17th. The 19th fret harmonic is still clear and bell-like though.

How is that possible? It's not a neck bow thing since they're harmonics and I'm not touching the fret board.

Can someone explain this to me?

And why do some harmonics come easier than others? 7th fret harmonics ring heaps better than 9th fret and 3rd fret harmonics are difficult at the best of times. Or is that just my own personal inability?

*bounce*
I really am curious

The wikipedia page is actually quite good. http://en.wikipedia.org/wiki/Guitar_harmonics

Also don't forget that harmonics are not *really* to do with frets, but to do with positions on the string.

So the 12th fret harmonic doesn't vibrate because its fret 12, but because its halfway between nut and bridge.

I only say this because you can't just count the frets from the 12th, as there is all that space between fret 22 and the bridge to take into account when dividing the string (if that makes sense). For example, 1/4 of the string is fret 5, and the equivalent is therefore 3/4 of the string, which isn't fret 17, its actually fret 24 (which is roughly 3/4 of the way along the string).

Check out the table in the wiki page for more details.

If I had to speculate I'd say that:

a) The different harmonics ring have volume when isolated that is proportional to the volume of that harmonic when the whole string is vibrating, this is consistent with the 2nd harmonic (octave) being a big part of the strings sound and being pretty loud when played alone.

b) The location of the nodes doesn't line up with the higher frets because (from memory) the frets are located for equal temperament which doesn't actually align with the overtone scale, at the higher frets the difference in position along the string would be amplified since the relative error of a small absolute distance is greater.

Eruera wrote:If I had to speculate I'd say that:

b) The location of the nodes doesn't line up with the higher frets because (from memory) the frets are located for equal temperament which doesn't actually align with the overtone scale, at the higher frets the difference in position along the string would be amplified since the relative error of a small absolute distance is greater.

Yep, and also fret positions are logarithmic (get exponentially smaller) where the harmonic points of the string are linear (evenly spaced)

sirvill wrote:Also don't forget that harmonics are not *really* to do with frets, but to do with positions on the string.

Yes, I know that.

But the frets are where they are because they need to be in those precise places, relative to the length of the string, in order to make the right notes.

I can see that it's a detail, a coincidence that I am playing a fretted instrument (as opposed to say, a cello) but the position of the frets is vitally important.

So I don't really understand why I can get a better harmonic from the 16th fret than from the 15th, especially when the instrument is not wildly out of tune on the 15th fret. It's just a harmonics thing.

Eruera wrote: b) The location of the nodes doesn't line up with the higher frets because (from memory) the frets are located for equal temperament which doesn't actually align with the overtone scale, at the higher frets the difference in position along the string would be amplified since the relative error of a small absolute distance is greater.

As far as I can understand that, it seems to make sense. Cheers.

Vince wrote: So I don't really understand why I can get a better harmonic from the 16th fret than from the 15th, especially when the instrument is not wildly out of tune on the 15th fret. It's just a harmonics thing.

I guess its because there is a harmonic node on about fret 15.9, and there isn't one on Fret 15 (there is one on fret 14.7 though, but its of a much lower order so it'll be more marginal).

The table on the wiki page is good, but this diagram explains it even better IMO if you're visual like me:
(http://en.wikipedia.org/wiki/Guitar_har ... _nodes.svg for big version)

I guess any easy way to explain the difference is that the harmonic nodes are symmetrical about the 12th fret, whereas the frets are not.

Eruera wrote:I guess any easy way to explain the difference is that the harmonic nodes are symmetrical about the 12th fret, whereas the frets are not.

Cool, thanks.

And thanks for the diagram, Sirvill!

That diagram is the bomb, awesome Sirvill.

My understanding is that as you divide the string up the power of the harmonic decreases. If you were able to place the pickup at the max amplitude (volume) point for each harmonic then you could hear those harmonics and their decreasing volume performance. On the standard guitar we usually have fixed pickups which see the harmonic at some other point that is not the maximum amplitude for all possible harmonics and therefore hear various volumes for them. Of course the string sensing aperture or window that the magnetic pickup has can vary too and that all plays a part in the magic we all love to talk about.