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The luthéal is a kind of hybrid piano which extended the "register" possibilities of a piano by producing cimbalon-like sounds in some registers, exploiting harmonics of the strings when pulling other register-stops, and also some registers making other objects, which were lowered just above the strings, resound. The instrument became obsolete partly because most of its mechanics were too sensitive, needing constant adjustment. The only pieces in the general repertoire to feature the luthéal are L'enfant et les sortilèges (1920–25) and Tzigane (1924) by Maurice Ravel.
The attachment was created by the Belgian organ builder Georges Cloetens, who first patented it on 28 January 1919 and named it the "Jeu de harpe tirée". Maurice Ravel used it in Tzigane for violin and piano, and in the opera L'Enfant et les sortilèges.
It generates a range of colours by adding two treble and two bass stops to a normal grand piano. These enable it to produce, in addition to the normal piano sound, additional timbres resembling cimbalom, harpsichord, and harp (or lute).
The luthéal was, in Ravel's day, a comparatively new piano attachment that had several registrations that could be engaged by pulling stops above the keyboard. One of these registrations had a cimbalom-like sound, which fitted well with the gypsy-esque idea of the composition. The printed version of the original score of the Tzigane piece contained instructions for these register-changes during execution. The Luthéal, however, did not survive: by the end of the 20th century the first print of the luthéal version of the accompaniment was still at the publishers, but the chamber version of the piece had long been performed in Ravel's alternative specification for the ordinary piano.
A surviving original luthéal was discovered in storage in the museum of the Brussels Conservatory and has been restored to playing condition. A new instrument was commissioned in 1987 by the French government on the occasion of the fiftieth anniversary of Ravel’s death, and is now in the Musée de la Musique, Paris.
Violinist Daniel Hope recently recorded a performance of Ravel's Tzigane that features a reconstructed luthéal, which Hope describes in a National Public Radio interview as "a cross between a typewriter and an organ that attaches to the strings of a piano" and produces "an amazing sound world." Violinist Chantal Juillet also made a recording with Pascal Rogé on piano luthéal, found on Ravel: The Complete Editions on Decca Records. 
- Cotte, Roger J. V. 2001. "Luthéal [Piano-Luthéal]". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
- Hugh Davies, "Instrumental Modifications and Extended Performance Techniques", The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell (London: Macmillan Publishers).
- 2008 interview: "The Glamorous Life Of Daniel Hope", NPR.org.
- "Ravel – The Complete Edition: Decca: 4783725", PrestoClassical.co.uk.
- Anon. 1973. "Séances de la Société: séance du jeudi 14 juin 1972". Revue de Musicologie 59:317. [Report on Roger Cotte, "Un instrument de musique peu connu, le luthéal, utilisé par Maurice Ravel".]
- Cotte, Roger J. V. 1976. "Le luthéal". Hi-fi stéréo: 221–24
- Davies, Hugh. 1988. "Maurice Ravel and the Luthéal". Experimental Musical Instruments 4, no. 2 (August): 11–14.
- DeVoto, Mark. 2000. "Harmony in the Chamber Music". In The Cambridge Companion to Ravel, edited by Deborah Mawer, 97–117. Cambridge Companions to Music. Cambridge: Cambridge University Press. ISBN 0-521-64026-1 (cloth); ISBN 0-521-64856-4 (pbk).
- Marcuse, Sibyl. 1975. Musical Instruments: A Comprehensive Dictionary. The Norton Library. New York: W. W. Norton & Company, Inc. ISBN 0-393-00758-8.
- "Pleyel Grand Piano with 'Luthéal' Mechanism". Musical Instruments Museum website (Accessed 17 June 2010).