Klaxon for Hire
This is an old instrument that was popular in the 1920's. The original klaxons were used extensively on early motor cars as the unique caaaw caaaw sound cut through the noisiest streets. The internal workings of the klaxon are complicated but basically a handle turns a metal impeller which catches against a sound chamber. The effect can be very different from each klaxon, as not all are constructed in the same way. Klaxons are only really used in recordings these days as the siren effect has become more popular within most areas of live and recorded music.