The contrabassoon is the wind instrument capable of sounding the lowest pitch in an orchestra. it is folded over several times to fit its impressive 18 ft length into a reasonable size instrument. the actual fundamental frequency of the contrabassoon is 27.5 hz. this means the model of the instrument as an open-closed tube is a bit too simple. but if you insist on using that model, what is the "effective length" of the instrument?