The wertmezer is a cheerfully comical two-player folk instrument which requires one player to play the keys and another to pump the bellows, thus producing a disjointed, harmonic blast: a "wert mezer" or "worst marriage." Originating in the rural divides of the Frigid River Valley, this unsophisticated, unwieldy instrument is the least respected member of the Z'Orchestra. Many musicians have argued that it does not belong in the Frobozz Philharmonic altogether.

In the Z'Orchestra, the wertmezers are found in the back row, stage left. The gederaglinis are to their right and the violins are before them.