dux
\Dux\, n. [L., leader.] (Mus.) The scholastic name for the theme or subject of a fugue, the answer being called the comes, or companion.
Where's Frigid and his Latin derivations/etymology of words
It's musical
and if you wanted to know what
Fugue is:
Music. An imitative polyphonic composition in which a theme or themes are stated successively in all of the voices of the contrapuntal structure.
...and if you wanted to know what
Contrapuntal means:
contrapuntal
adj. Music
Of, relating to, or incorporating counterpoint.
and lastly
counterpoint
n.
1. Melodic material that is added above or below an existing melody.
2. The technique of combining two or more melodic lines in such a way that they establish a harmonic relationship while retaining their linear individuality.