We don't have synonyms for flugel yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are flegel, fluegel and alugel.
(n) :
Alternative form of flugelhorn. [A brass instrument resembling a cornet but with a wider, conical bore, and usually with three valves, in the same B-flat pitch as many trumpets and cornets but with a more deeply conical mouthpiece than those. A bugle with valves.]
(n) :
Alternative form of flugelhorn. [A brass instrument resembling a cornet but with a wider, conical bore, and usually with three valves, in the same B-flat pitch as many trumpets and cornets but with a more deeply conical mouthpiece than those. A bugle with valves.]