Both Uses

flourish
in
The House of Mirth
(Auto-generated)

It was a large disjointed hand, with a flourish of masculinity which but slightly disguised its rambling weakness, and the words, scrawled in heavy ink on pale-tinted notepaper, smote on Lily's ear as though she had heard them spoken.†
Chpt 1.9
Ten months earlier the amount it stood for had represented the depths of penury; but her standard of values had changed in the interval, and now visions of wealth lurked in every flourish of the pen.†
Chpt 2.13 *

Definitions:

(1) (flourish as in: the business is flourishing)
to thrive (grow or develop well)
(2) (flourish as in: dismissed them with a flourish)
a showy gesture

or:

the act of waving -- a hand or an item
(3) (meaning too rare to warrant focus)
In Shakespeare's plays, flourish is often used as a stage direction indicating a specific type of showy gesture: fanfare played by trumpets or other horns to announce the entry or exit of royalty.

Check a comprehensive dictionary for other senses including some that are of interest to musicians.