I've been reading Mattheson's Der vollkommene Capellemister and written about it a bit in my blog in the entries Mattheson on Perfection, The Location of Paradise Revealed, The Origin of Music and What you really need to know about Angles. Today I'm reading chapter six, and I love how he writes about the need for good posture:
Can the attentive listener be moved to pleasure if he [....] sees a dozen violinists who contort their bodies as if they are ill? If the clavier player writhes hsi jaws, wrinkles his brow, and contorts his face to such an extent that it could frighten children? If many of the wind instrumentalists contort or inflate their facial features (one must not omit the lips of the flutist) so that they can bring them back to their proper shape and color in half an hour only with difficulty?
It is even said of Minerva, that she threw the flute away just because wind instruments have the misfortune that they distort the features; and is also known from history that Alcibiades, though he was otherwise a great lover of music, nevertheless hated flute playing for the cited reasons. The viola da gamba would have pleased him more: For there is, after the lute, hardly any instrument with which one can produce a more refined posture. Because of this, the French love both instruments before all others, since their strong inclination toward the bon air often goes so far that their zeal makes them seem comical.