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I've been learning this John Renbourn song (The Hermit). There's loads of harmonics which has reminded me of a question that's cropped up for me before and I don't know the answer.

I've got two newer (under 20 years old) Martin's kicking around a D-18 (spruce/mahogany dreadnought) which is my favorite acoustic guitar, and my dad's M-36 (spruce/rosewood 3pc back, smaller bodied but not OM/OOO size).

I can get harmonics to ring at the 12th, 7th, and 5th fret no problem, and doing the harp thing works too, but there are a few harmonics in this song at the 9th fret on the low E and A string. I first sat down with the song with my dads guitar, it was close at hand and I didn't seem to have any trouble getting those harmonics at the 9th fret to ring. Today when I went to practice, I was down in my shop/studio and grabbed my D-18, everything was working the guitar sounded great, but those harmonics at the 9th fret were ghosts.

So, what goes in to making a guitar's harmonics ring? It's obviously not a case of good guitar vs bad guitar.

My first thought was intonation (better sympathetic resonance), but I don't think any other strings have harmonics matching those, so it must be something else. I assume your strings are in good condition? That can certainly kill those higher harmonics. Seems unlikely that it would be lack of resonance from the soundbox since the frequencies are still relatively low. But try playing the same notes on the high E string (4th and 9th frets) and see if they sound louder or quieter or decay differently than other notes.

What do you mean by the harp thing?

Lack of harmonic might be that you are holding one of the guitars so that you are accidentally plucking at one of the nodes for that harmonic. If you pluck on the node, you cannot activate the harmonic. Try plucking closer to the bridge.

As W Bergman says it matters a lot where you pluck. On my classical I need to pluck pretty close to the bridge.

Also the same harmonic is available on the 4th fret. Could you use that one instead? Renbourn was a devil for using harmonics. I often used to play the notes straight.

Dave M

The intonation on the D18 seems okay. The worst offending string (the G) is 4 cents sharp. But even if it was an intonation issue wouldn't adjusting my fretting hand deal with that? The strings are a couple days old. On the high E its even harder to get those harmonics.

I tried again this morning focusing on those harmonics but used a pick instead of my fingers, (When I play fingerstyle I prefer the sound of the pads of my fingers to finger nails or picks) I can get a louder harmonic with the pick. The 9th and 4th fret are still much quieter than the other harmonics, but that seems more like the nature of the beast. Still the smaller rosewood guitar is much more lively with the harmonics, and the strings on that guitar are dead!

Oh, I just meant that I can fret a note and get the harmonic 5, 7, or 12 frets above using my thumb and finger. (But I realize that is not entirely the harp technique.) I just said that to show that I don't usually have issues with getting harmonics. However I usually stick to the obvious choices and haven't experimented with less common harmonics like the 9th or 4th fret...



I've never really thought about this, is there a way to know where the corresponding nodes are to different harmonics? Does each fret have a different node? Also, along a similar note, I've noticed that when using the neck pickup on a stratocaster electric guitar the harmonics are almost non existent compared to other electric guitars. Would the pickup being under a specific node negate the harmonic when that pickup is active?

Cool, I'll keep that in mind.

The 9th fret harmonic is in a run of 16th notes all around the 12th and 11th frets, so getting to the 4th would be pretty tricky.

You play a harmonic by touching the string at a node to dampen all the other frequencies. You touch the string at the node closest to either the nut or the bridge. The nodes for each harmonic divide the string into equal whole number segments that vibrate alternating directions and leave the node motionless. If you touch the node closest to the nut or bridge, you kill all other harmonics, because none of them will share those nodes, except on octaves.

The first harmonic node is at the 12th fret, and is an octave. It divides the string into two equal parts. The second harmonic nodes are at the 7th and 19th frets, and divide the string into three equal segments. The third harmonic has nodes at the 5th and 12th frets and also somewhere out over the sound whole that you can find by trial and error. The third harmonic is two octaves. Notice that the first and third harmonics share a node at the 12th fret, so to get the third harmonic only, you need to touch one of the two nodes closest to the nut or bridge.

Every harmonic but the first has more than one location, corresponding to a node, where you can touch the string to force that harmonic. So, you can find those by trial and error and use the one most convenient or one that seems to react best on your guitar.

If you pluck at a node, you are causing the string to move at exactly the location that should me motionless—so you will not get a harmonic. Plucking near the bridge reduces the chance that you accidentally are plucking at a desired node.

I did notice that some strings that are not manufactured to have uniform weight along the string sometimes cannot make harmonics, or be tuned properly, either. Decades ago, the Augustine black label classicals had defective “b” strings that were awful. I would buy extras and try five or six to get one that was tolerable. I do not know if the black label still has that problem. Nylon guitar strings can be done on a manufacturing run to store in the warehouse for long periods. So, there is even a chance that your problem is from a bad string.

Intonation affects more than just the notes being actively played. For example if you play the 7th fret harmonic on the low E string, you get the same frequency as the open B string. If both produce the exact right frequency you'll get strong sympathetic vibration (the open B will boost the volume of the harmonic you played). If one is a little sharp and the other is a little flat, then the open string won't activate as strongly. And it's not only open string frequencies; all harmonic frequencies on all strings (including fretted ones) can resonate as well. Say you play the 3rd fret on the A string (note C), then 3x that C frequency (harp thing at 10th fret) matches the 12th fret harmonic of the open B, so that frequency will resonate. The higher the harmonic, the more sharp it will be, but with better intonation you can get more of them close enough to activate.


Sorry, I meant play fretted notes on 4th and 9th frets of high E. Those frequencies match the 4th fret harmonics of the low E and A strings, so it will allow you to hear if the box is having any wonky resonances at those specific frequencies. Also try it with all the other strings muted, to eliminate their resonant contribution.

I think the 16th fret gives the same harmonic as the 9th. Try that and see if it works and if it fits your technique better. I spent a lot of time just by trial and error to find my best way to touch the nodes for harmonics. I think there are a lot of different techniques.

Also, I was a bit too general in saying that you always need to use the node closest to the end of the string. As the harmonics get to the high overtones, there are lots of nodes.

My last 2 cents (I hope).

You mentioned that you prefer to play finger-style. If you have not already developed the following technique, work on it. It takes time, but then it is mastered like other things.

Stop the node with your right hand index finger and pluck with the thumb or ring finger on the same hand. You can search and find a node for the 9th fret harmonic also somewhere around the side of the sound hole closest to the bridge--probably real close to where you usually hold your hand to play.

This method also works when you want to play harmonics off a fretted note. For example, fret the F on the E string and you can play the harmonic on the 13th fret (or 6th or 8th, etc).

_________________
Steve Smith
"Music is what feelings sound like"