Article: Converting to 7-string
adding an octave G string for pseudo-12-string sound.
Roger McGuinn approached the C.F. Martin Guitar Co. with an
idea for a unique 7-string guitar that would capture the essence of the 12-string
still lend itself to single note runs and bends that are problematic on a
12-string. They made him one, and since have issued the HD7 custom 7-string
My customer had seen the Martin HD7 Roger McGuinn guitar, but didn't want to spend that kind of money. So he brought me this LoPrinzi dreadnought and asked if I could modify it. It's a well-built guitar and not such a rare gem that would be a crime to modify. The bridge is deep enough to handle the added pin hole, and the bridge plate is certainly beefy enough to handle the added pull. We're not really adding much stress to the top, just the one string. (The D'Addario package says a .010 string at pitch adds 22.9 pounds of pull.)
Next, we had to decide what to do with the extra tuner. The Martin has four machines on the treble side of the peghead. To do that, I'd have to fill the three existing holes and replace the veneer to cover the patches, and that would still leave patches on the backside to cover somehow. So I proposed adding a banjo-style peg, and we agreed this was the best way to go.
Here are some photos of the whole process.
That nice, flat belly is crying out for another pin hole.
Here's the bridgeplate reflected in my inspection mirror. It's pretty massive. You can also see where stick-on pickups have been on there.
I'm holding the banjo peg I'll use; gold with an ebony button matches the others pretty well.
Too late to turn back now! The other tuners were off when I drilled this on the drill-press. I clamped the headstock to a board so the wood wouldn't chip when the bit exited the back.
The bridge is done; hole drilled, tapered and chamfered.
Instead of replacing the nut, I deepened the G slot and inlaid a piece of bone. Once the two new slots are cut, the inlay will be invisible.
The tuner is on.
That's a lot of gold.
Here are the paired Gs in the nut.
I liked the contrasting bridge pin, but he's going to get a pin to match his bone pins. I dubbed the guitar the Hi/LoPrinzi!
postscript: The weekend after I delivered the Hi/LoPrinzi, Margie and I played a gig with the owner. He used it on every song; he loved it; and nobody came up and said "What the @#$! did you do to your guitar?!"
post-postscript: The nut didn't hold up. While changing strings,
he knocked the little fillet out, so I made a new nut for the guitar after
all. Serendipitously, that solved an intonation problem on another string.