The Kertsopoulos Pneumatic Foot Pedal Guitar

Alas, not a harp guitar as I had inferred, but still an amazing invention that opens up an entire new world (at least to me!).  In a nutshell, all the extra strings and bridges and bars and levers and pneumatic gauges are for the purpose of applying the pedal effects of the piano to the guitar.  At least that’s what I think!  I’d love to hear what Al Carruth makes of all this cleverness.

This story started with a blog about a week ago, when the instrument was spotted (by Tom Shinness) on the Facebook page of Smaro Gregoriadou.  The builder – Yorgos Kertsopoulos – somehow spotted it immediately and has written me a nice series of emails.  He can explain it much better than I (I still have to see it work to understand it!).

His site and links to his many photos and articles are exhausting (now I know how my own site affects people!) – but I sense that they’ll appeal to many of you in the harp guitar community.

Have fun, and if you figure it out, let me know!

From Yorgos:

Hi Gregg,

Thank you very much for your kind words concerning my work and for the beautiful posting you have made for my guitar.  Please note that if you would like to see in detail the guitar you have posted, I have made a specific blog exclusively for it and the link is:

Also, please note that my official website is:

It will be a pleasure to hear more from you and please feel free to contact me concerning any more required info.  Congratulations also for your wonderful work, which I will in time like very much to explore through your site.

All best,

Hello again Gregg,

In case it is of interest to you I send you below the two links concerning two articles I have written concerning my work at Guitar International.  I am writing a series of articles for the magazine on my work entitled: “Kertsopoulos Aesthetics”.  In a few days part 3 will be published.


Hi Gregg.  Thank you for your interest in my work and for your kind words.   To answer to your well defined questions, there are many functions assigned and also obtained from the extra strings, namely:

1) By using only six extra strings in and out and around of the five in all bridges, we obtain 21 different vibrating string lengths, which we tune to the desired (specific for each string) tuning, according to the needs and we are also able to play these strings according to the musical needs.

2) The two levers that move up and down by the pneumatic system  (through the needle that pushes them upwards with adjustable force by the pedals) apply the desired pressure-force specifically to nine string lengths. This function is responsible for the pedal effects on the guitar. The centered lever is stable to provide the necessary stability to the system.

3) As the strings pass under one main bridge and come up through the other bridge, they apply an upward torque force on the soundboard compensating for the extra downward torque forces that are exerted mainly on the soundboard itself and consequently to the sides of the instrument.They are engineering solutions resembling the flying bridge’s design, very necessary to provide a dynamic equilibrium for the static as well as the vibratory state of the instrument.This is also essential for the smooth effect of the pedal mechanisms.

4) As the 21 string lengths are tuned to specific frequencies they enhance the Helmholtz resonant frequencies of the chamber as well as the frequency response of the plate’s tuning areas (top and back included) according to taste, because these can differ and can have a great variation in the range of the performer’s taste.

5) They are also used as sympathetic strings in real time playing and they have a wide range of frequency adjustments.Please note that function 4) is a separate function differing from function 5).



    Hi Gregg,

    Below are two links to two recent articles of Guitar International that might be of interest.

    All best

    Kertsopoulos Aesthetics: The How and the Why – Part 3
    “The Kertsopoulos mathematical model and geometrical progression of the classical guitar, presented for the first time in such a detail.” Vol. 1 of 7.

    Smaro Gregoriadou: Reinventing Guitar
    Guitar International recently sat down with Smaro Gregoriadou to talk about her latest album, the instruments she’s playing on the record and get her thoughts on the modern, classical guitar scene…


    Hello Gregg,
    below is the link of a recent article of mine published by Guitar international concerning the golden ratio and the golden rectangles in relation with the “Kertsopoulos mathematical model of the guitar”, all best Yorgos

Leave a Comment

The Harp Guitar Foundation            The Harp Guitar Gathering®

History          Players         Music         Luthiers         Iconography         Articles 

 Forum                 About                Links                Site Map                Search               Contact

All Site Contents Copyright © Gregg Miner, 2004,2005,2006,2007,2008,2009,2010. All Rights Reserved.

Copyright and Fair Use of material and use of images: See Copyright and Fair Use policy.