IMO, The Psychology of Man's Possible Evolution - Ouspensky (Gurdjieff's disciple)- a little over 100 pages, has interesting views that could the help musicians and pianists into inner experiences, movements, technics of ATTENTION and Self-Observation.
It could be helpful to the improve piano performance.
Gourdjief and Ouspensky ideas touch important aspects of movements, automation and it's relation to abdominal brain and The Psychology of Man's Possible Evolution is a short introduction to the psychology of an extensive 'system for personal development' -
https://www.amazon.com/gp/product/0394719433/104-1534269-6835966?v=glance&n=283155&s=books&v=glancePiano pieces of music provided by Gurdjieff and harmonized and notated by de Hartmann are an good option when if you are seeking something "unusual".
Philosopher, seeker after the truth, reconciler of science and religion, teacher, guru to artists, writers and musicians, Gurdjieff was an enigmatic figure; even his birthdate is uncertain: 1866 or 1877. He taught movements "to alter or heighten consciousness" at his Institute for the Harmonious Development of Man, located outside Paris---a highly improvisatory process for which he composed equally improvisatory music.
Author of Meetings With Remarkable Men (also avaiable in video)
https://www.amazon.com/gp/product/0140190376/104-1534269-6835966?v=glance&n=283155&s=books&v=glanceListen this beautifull song - "Wooman's prayer " at :
https://www.amazon.com/exec/obidos/ASIN/B0002ONC72/qid%3D1128779398/sr%3D11-1/ref%3Dsr%5F11%5F1/104-1534269-6835966Some links about Gurdjieff:
https://www.recordsinternational.com/RICatalogJan00.htmlhttps://www.musicweb-international.com/classrev/2002/May02/Gurdjieff.htmhttps://www.cduniverse.com/search/xx/music/pid/6764559/a/Gurdjieff%2FDe+Hartmann:+Music+for+the+Piano+Vol+2.htmhttps://www.cduniverse.com/search/xx/music/pid/2350776/a/Gurdjieff%2Fde+Hartmann:+Piano+Music+Vol+3+%2F+Alain+Kremski.htmhttps://www.amazon.com/exec/obidos/tg/detail/-/B00005Q68K/ref=pd_bxgy_img_2_cp/104-1534269-6835966?v=glance&s=musichttps://www.amazon.com/exec/obidos/tg/detail/-/B00003CK7L/ref=pd_bxgy_img_2_cp/104-1534269-6835966?v=glance&s=musicSome Gurdjieff's aphorisms:
https://www.gurdjieff.org/aphorisms.htmRemember yourself always and everywhere!
Consider what people think of you-not what they say!
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Try to remember yourself when you observe yourself!