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Martin / OM21 Adirondack 49mm Neck Double G String / Guitar For Sale

Martin OM-21 Custom Adirondack 7-String acoustic guitar probably from the early 2000s (serial number is obscured by battery compartment). This is by no means a standard OM-21. Custom factory features are an Adirondack spruce top with beautiful grain and wide neck with 48mm (1 7/8") nutwidth. Aftermarket features include a built in pickup and the main attraction; an added 7th string. For some of you this feature might ring a bell because in the early 2000s, Roger McGuinn (12-string magician, the Byrds) worked with Martin to develop a seven-string folk guitar. The guitar they developed (HD7 Roger McGuinn signature) augmented the G (third) string with an extra high octave string. This is exactly what the extra string on this instrument does. On the headstock an extra banjo tuner was added, and the bridge has an extra hole and bridgepin to accomodate for the extra string. It might seem a small addition, but the extra string truly adds that 12-string jingle to the overall sound without it being bothersome for the playability. Other features include Indian Rosewood back and sides, tortoise bindings, rosewood bridge, rosewood fretboard and 6 regular closed back Martin tuners. 645mm (25 3/8") scale length, 48mm (1 7/8") nutwidth and 61mm (2 3/8") string spacing. Includes original hardshell case.

The Fellowship Of Acoustics, Netherlands  

Contact name:
The Fellowship of Acoustics
Martin, Gibson, Fender, Vintage Guitars, Santa Cruz, PRS, Collings, Rozawood, etc..
English, Dutch and German
Fine, Vintage and Rare Guitars
Opening hours:
Monday - Saturday: 10am - 6pm.


I have always been opposed to being trapped into a job eight hours a day to purchase the free time to do what I enjoy. That’s why i started the Fellowship of Acoustics. The fellowship of acoustics was founded by Rudi Bults, Guitarist and obsessed with tone and wood. The idea was offering real expertise when trading and selling the finest instruments in the world from our showroom in Bergentheim, Netherlands. Helping others find the right tools and enjoying an atmosphere that’s unhurried, honest and informative that’s my go. We are nothing like the "supermarket" style music stores, but specialize in string-things only. We are widely known for Flattop guitars but also sell electric, mandolins & banjo’s, amps, parts, and accessories. Our store has earned the reputation for being a great place to shop for the best products and service.
It is our hope that this new website - much more than a list of "gear" for sale - will serve as an example of our commitment to offering a more personal approach, a friendly atmosphere, and an ultimately more satisfying experience for our friends and customers.
If you have any questions just dial +31-523-232205 or e-mail My name is Rudi Bults, and I’m always here to help out. Wherever possible, we would recommend that you visit our store and experience our instruments and service first hand. However, because of our high standards you can be confident of ordering online from us. We hope you enjoy your visit to our site, and welcome your feedback.


We do speak English, Dutch and German! Feel free to call in any of these languages and ask your questions! Call 0031-523-232205




We LOVE Guitars, and buy and trade for most stringed instruments. But we also do consignment, make appraisals for insurance or put you on our watch list. Please check the Buying & Trading page for details.
The Fellowship of Acoustics BV
Kanaalweg oost 36
7691CE Bergentheim
To order online: go to
And choose your Guitar and purchase through the website.

Available methods of payment
# Paypal
# Credit Card (MasterCard/Visa/AmEx) only available for European Community and USA.
# Bank-Wire transfer

Call for Online Order+31(0)523-23-2205
our policy:
14 day money in return return warranty  Shipping cost, and Customs & import return costs -bothways- are buyers responsibility
1 year Guarantee on Used Guitars
5 years Guarantee on New guitars (or 'limited lifitime' if the Builder guarrantees such)

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