There are several synonyms for the term "bass horn" out there. For example, a "tuba" is a large, low-pitched instrument with a bell-shaped opening and valves. It is typically made of brass, and its sound is often used in brass ensembles and orchestras. Another synonym is "euphonium," which is similar to the tuba, but has a slightly different tone and range. Other synonyms include "bombardon," "sousaphone," and "baritone horn," all of which are low-pitched brass instruments that can add depth and richness to a musical performance. Each of these synonyms has its own unique characteristics and sound, making them valuable additions to any musical ensemble.