Both Uses

solemn
in
1984, by Orwell
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He wolfed another tasteless meal in the canteen, hurried off to the center, took part in the solemn foolery of a 'discussion group', played two games of table tennis, swallowed several glasses of gin, and sat for half an hour through a lecture entitled 'Ingsoc in relation to chess'.†
p. 109.3

solemn = very serious--possibly dignified
His face grew solemn again, and he raised his glass: 'I think it is fitting that we should begin by drinking a health.†
p. 171.2 *

Definitions:

(1) (solemn)
in a very serious (and often dignified) manner
(2) (meaning too rare to warrant focus)
Less commonly, solemn can mean that something was done with great or appropriate ceremony. It can also be used to describe something as dark or undecorated.