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Martin FX640 Light 80/20 Bronze Acoustic Guitar Strings

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Martin FX640 light acoustic guitar strings use a thinner core wire to deliver greater player control with sharp attack, increased flexibility and improved harmonic sustain. Martin FX strings have a w... Click To Read More About This Product

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Martin FX640 light acoustic guitar strings use a thinner core wire to deliver greater player control with sharp attack, increased flexibility and improved harmonic sustain. Martin FX strings have a wrap that is constructed of 80/20 bronze and the core wire is Martin's platinum: high carbon steel with special zinc flashing. Recommended for lead acoustic rock and fingerstyle playing styles.

80/20 Bronze

This alloy is comprised of 80% copper and 20% zinc. It is popular for acoustic strings and provides a very brilliant tone when they are initially put on the guitar and mellow over time.


High carbon steel with special zinc flashing that gives the wire better tensile properties. Martin uses platinum on the FX string sets to increase the durability and improve harmonic sustain.

It has been said that the guitar becomes a mini orchestra when played fingerstyle. In fingerstyle's simplistic form, the thumb is setting the beat and the fingers are working through the melody. While that sounds rather basic, it is rather challenging to master. Despite all the instruction and guidance on fingerstyle playing, very little focus has been given to the string where the sound is truly initiated. So, Martin started from scratch in their string research facility and worked with several fingerstyle groups to develop a string that would be more responsive to fingerstyle methods. After creating many samples in the lab and working with the fingerstyle groups, they determined that a fingerstyle string should deliver crisp, clear notes with little overtone and light sustain. The string needs to be flexible and almost soft to the touch, but very controllable. And, since fingerstyle playing is not a forceful style, the string needs to deliver the proper resonance and vibration to the top to create the right volume.

The end result: Martin FX Flexible Core, available in 80/20 Bronze for maximum brilliance out of the box, and 92/8 Phosphor Bronze for warmth and consistent brilliance. The silvered steel plain strings provide the traditional tone and longevity you expect from Martin. The zinc flashed thinner core wire and thicker wrap wire increase the resonance and control while creating a more flexible string. Ultra-pure high tensile strength steel has been chosen to maximize the durability of the string.

Martin asked a member of the Michigan Fingerstyle Guitar Society to give them his feedback on the Martin FX strings. Here is Dave Wodnicki's experience: "The new Martin FX strings are truly a great set of wires. On the sound, the tone is clear/warm and they ring very nicely. On the feel, great to the touch but what I really noticed was that when I played up above the 7th fret all the way up to the 14th, it took less effort to make the chords, runs and bass lines. I was able to move around a bit easier and the control was very solid, which means I had plenty of reserve energy for expression. That's exactly what I like because there is a lot of music up there when you can get some real power into the phrasing and sustain it. The Martin FX Phosphor Bronze strings are perfect for fingerstyle. Nice work, guys!"

Whether you play Travis picking, American primitive guitar, ragtime guitar, Celtic guitar, slack-key guitar, percussive fingerstyle or jazz fingerstyle, give Martin FX Flexible Core strings a test. The Martin FX Flexible Core sets are also suitable for beginning guitar players. The FX line requires less finger pressure to play than standard strings at equivalent tensions. The thinner core wire also provides better sustain in the upper harmonic overtones.

C. F. Martin & Co., Est. 1833 remains one of the longest surviving family owned and operated manufacturers in the world. Six generations of the Martin family have been dedicated to the company's products, their superbly well-crafted acoustic instruments and strings.

  • Gauge .012 - .054
Pro Coverage
One year warranty on Martin Backpackers, Little Martins and Ukuleles. Limited lifetime on other Martin guitars.

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Review Snapshot

by PowerReviews
MartinFX640 Light 80/20 Bronze Acoustic Guitar Strings

(based on 2 reviews)

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Reviewed by 2 customers

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(2 of 2 customers found this review helpful)



By Rodent


Comments about Martin FX640 Light 80/20 Bronze Acoustic Guitar Strings:

I just bought a set of these strings for the first time and strung up the old Alvarez. I was amazed right off the bat. I am most often playing electric guitar but recently I've been playing acoustic with some frends after work and my biggest problem is that I can't switch from playing electric to acoustic and play very well. I struggle with the acoustic due to the lack of playability. When I installed the FX strings there a huge difference in the way the guitar plays for me I couldn't be happier. To think I was gonna get rid of this guitar to get one with a shorter scale to help with this problem. Now I think I'll keep it and save some cheese to spend on a new Tele.

(2 of 2 customers found this review helpful)


Soft on the Fingers

By Lynn Thomson

from Boise, Idaho

Comments about Martin FX640 Light 80/20 Bronze Acoustic Guitar Strings:

I recently put these strings on my Parkwood acoustic, and what a great sound. The blend of high and low is just right for fingerstyle. The bass strings sound great and the higher strings don't overpowerthe bass like some strings do. I started playing three years ago after a 40 year hiatus. I never really learned fingerstyle guitar playing until now. These strings make it so much easier on my 65 year old fingers that I can play for a couple of hours each night. I would highly recommend these strings to anyone looking of ease of play without sacrificing quality sound. I have a Washburn classical and a 1978 Hohner dreadnought so I can play all types of music. I have a set of Martin light phospherous bronze strings that I plan to put on my Hohner, again looking for a lighter, softer string for strumming.

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