harmonics

[HOF dad]

I have a question about harmonics.
Not how to play them (I'm good there) but how easily they are played and how strong / loud they can be on one guitar versus another.
I just took my every day player (Taylor 414) in for a quick check up and to lower the action a little.
While it's been in the shop, I've pulled out a few older case queens to play: mid 70's epiphone jumbo, and an ovation pinnacle.
The epiphone and ovation are both WAY easier to pull harmonics from than the 414. I can also get a louder harmonic sound - especially from the ovation - on these two.
Heck, I can get harmonics off the 9th fret of the ovation.
So.....it makes me wonder why the difference. What is it in the build, or wood types, or set up that can allow for a better harmonics.
Is there any way to improve that on a guitar?

[FrankHudson]

Like you I don't know. When your post caused me to think about the question i came up with a few unverified theories/things I may have observed.

Do new strings seem to have louder harmonics? They seem to have more of the "natural" overtone series to a "normal" note, even to an excess when fresh.

Some guitars respond better in certain registers and to certain kinds of note attack. So. a guitar with better response to a lighter touch, or more treble response would seem to give a more apparent response to harmonics.

Unsure that scale length impacts this. Do longer scales have louder harmonics? I play a lot of "artificial" harmonics off the side of the pick on electric and Fender scale instruments seem favor this, but that could also be the generally higher treble response of Fender pickups.

Months with R in them, day of the week, lucky socks. At least with me, some techniques seem to come easily some days and not others. We may think it's the guitar, but it may be coincidental.

[JonPR]

I can't think of any logical reason, other than perhaps the state of the strings. I suspect it's easier with new strings.

You do have to make sure you're picking in the right part of the string, not just touching in the right position. Normally it's safest to pick close to the bridge, but if you want to calculate the best picking position, it's always in the middle of whatever fraction of the string is being sounded. (Scale length makes a difference with actual measurements, but not much.)

E.g.,

1/2 string length (octave harmonic), fret 12. Pick at 1/4 string length from bridge (midway between bridge and fret). Of course this one is pretty easy anyway, it's just about the principle!

1/3 string length (octave + perfect 5th), frets 7 or 19. Pick 1/6 of string length from the bridge (roughly 4").

1/4 string length (two octaves), fret 5. Pick at 1/8 string length from the bridge (3")

1/5 string length (2 octaves + major 3rd), frets 4, 9, 16. Pick 1/10 string length from the bridge (2.5").

And so on. With care you can get a few more harmonics with touch points between frets 4 and 2 - picking closer and closer to the bridge, but of course they are increasingly fainter and more difficult, and hardly any practical use. (E.g. 1/7 string length is a note seriously out of tune with the nearest correct note.)

And btw, although the 1/5 harmonics can sound cool, don't tune to them. If you get your string exactly in tune, you'll notice the 1/5 harmonic registers flat - it's supposed to. The equal-tempered system needs a tuned major 3rd to be 14 cents sharp of the harmonic, so the harmonic will read 14 cents flat.

The 1/3 harmonic is also out of tune, but only by 2 cents, and tuners won't register that. (When you pick a string it actually goes sharper than that anyway, just from the stretching action caused by its vibration, before flattening slightly as the vibration reduces.)