As far as music, I would recommend Chopin, Brahms, or Liszt, for piano, or some piano concerto from Rachmaninoff. Maybe you could also take a keyboard with you, put airplane on autopilot, and practice piano playing.
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Alternatives, are (maybe) knitting socks, playing chess with ATC, I personally recommend you games of cards for convenience, besides playing the music. If you get bored, go jogging on the wing, but a parachute is suggested.
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Sorry Eikido, no experience with the above, but I am certain you should inquire for ATPL training at the Stockholm or Goteborg music academies.
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I have a Bosendorfer concert grand piano at home... nearly 100 years old, but I plan to update it with FMC to read the music. Just heavy to pack it with my flight kit.
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Happy contrails on a rhapsody...