The term 'sousaphone, e.g.' can be solved by the four-letter word 'TUBA'. The sousaphone is a type of TUBA, which is a large brass instrument that produces a deep, rich sound. It is typically used in marching bands and other large ensembles. The sousaphone was designed by John Philip Sousa in the late 19th century and is named after him. It is characterized by its large bell and curved shape, which makes it easier to carry while marching.