I am not a teacher.
I couldn't find any italic text, so I'll just help you with the first piece of bold text.
I don't think the author was referring specifically to Arabesque by Claude Debussy, but rather to the fanciful style of music known as arabesque. This typically involves ornamentation which the 'mild drifting' of the fingers on the piano keyboard could evoke, but with which the author's character does not agree.
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