helicon, a large, valved bass brass instrument that is a member of the tuba family. Developed in 1845 by Ignaz Stowasser of Vienna, it has a spiral circular form that allows the helicon’s bell (the flared end of the instrument) to rest on the player’s left shoulder and, thus, makes the instrument relatively easy to carry in marching or horseback military bands, for which it was designed. The helicon was the basis of the sousaphone—named for its inventor, American bandmaster John Philip Sousa.