making an octave instrument out of an already existing mandolin?

I imagine that someone must have done this already, so I wonder if I could ask here. If I wanted to tune a regular mandolin like a 12-string guitar, so to speak, what kind of strings could I use for the octave-lower ones? And is it a good idea to do this all the way through, or is it better to leave the top one or two courses in unison? Thanks so much.

Tuning something like that would be a nightmare. I don't know why but I have heard very few 12 string guitars that were in tune. That octave plays havoc with tempered tuning IMHO

Never gonna happen.

You can do octave pairs on the lower courses with one string each tuned to standard G and D and one tuned an octave HIGHER. There is no way on God's little green earth you will ever successfully make an octave pair on a standard mandolin with one string tuned standard and the other tuned an octave LOWER.

What they said. Octaves of much-shorter-than-guitar-length scale tend to go out of tune quickly as you move up the neck, as evidenced by occasional comments here on Martin's tiple design, which is sort of a cross between baritone ukulele and 12-string guitar (and has 10 strings).

In other words, 12-string guitars, IMHO, don't get too badly out of tune as you go up the neck, but on much shorter scales (tiple is 17") the octaves get not-so-great by even the 5th fret. Mandolin is just under 14", so...

But strings are cheap, and sticking G and D octaves on there just for fun should be, well, fun, and probably instructive. You can do them experimentally w/out changing the nut slots, but adding LOW octaves to the A and E strings, if that's what you meant, could require modifying the nut: yuck!

My plan is, and maybe your should be, to super-compensate the saddle so that all will be harmonious... but not tonight!

Quote:

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Originally Posted by EdHanrahan

...Octaves of much-shorter-than-guitar-length scale tend to go out of tune quickly as you move up the neck, as evidenced by occasional comments here on Martin's tiple design, which is sort of a cross between baritone ukulele and 12-string guitar (and has 10 strings). In other words, 12-string guitars, IMHO, don't get too badly out of tune as you go up the neck, but on much shorter scales (tiple is 17") the octaves get not-so-great by even the 5th fret...

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As the owner of two tiples, agree wholeheartedly.

Some mandriolas -- which are twelve-string mandolins, with four courses of three strings each, were tuned with the "middle" string of each course an octave lower. Not a successful experiment.

Longer-scale octave mandolins, and bouzoukis, are quite frequently put into "octave" tuning, especially on the lower string courses. I have a Regal Octofone where I've tuned the third and fourth, D and G, courses, in octaves. But it has a scale length eight inches longer than your mandolin.

Even a 12 string guitar keeps the E and B strings unison and not octave until the wound strings

A lot of the black country blues players like Howard Armstrong, Carl Martin, Charlie McCoy and Bogus Ben Covington used octave courses at one time or another.

Others using octave-strung mandolins have been Fiddlin' Doc Roberts, Yank Rachell, and Charlie McCoy IIRC.

I'm not saying they were right or wrong to do so, but clearly some did found some success with the idea.

you need a longer neck to go an octave down ..

but a Gg Dd aa ee which is one of the Irish Zouk tunings is possible up in the standard violin range.

it's often done on citterns, for best results you need to compensate the nut, same for 12 string guitars. ed myronik in vancouver used to be a genius at this but he's getting pretty old and ill.hard to find some one who does it here.