Both Uses

muster
in
The Mysterious Benedict Society
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The girl, frightened and perplexed, could hardly muster a shake of the head.†
p. 19.3 *
"Oh, yes, sir, very much!" cried Reynie with as much enthusiasm as he could muster.†
p. 236.9

Definitions:

(1) (muster as in: muster strength or the crew)
to gather
The exact meaning of this sense of muster is often subject to its context. For example:
- "mustered her courage/strength/a smile" -- to gather from within
- "muster the soldiers/crew" -- to gather -- typically for inspection
- "muster volunteers/votes" -- to gather enough to do something
(2) (muster as in: didn't pass muster)
inspection -- especially of soldiers or a crew
(3) (meaning too rare to warrant focus)
More rarely, muster can refer to a counting or census. Much more rarely, muster can refer to a call to duty such as compulsory military service or jury duty. In that sense, you may see the expression muster in or muster out. Still more rarely, a muster can refer to a group of peacocks.