The tuba is the lowest member of the brass family, often reading music ledger lines below the bass clef. Unlike the string bass, it is not a transposing instrument. As the largest brass instrument, it is the least agile of its family, and rarely plays fast runs outside of solos.
The timbre of the tuba is rich and powerful. When playing loud, accented passages, the tuba can be clearly heard through the texture.
When writing for the tuba, it is typical to give the instrument the root of a chord. As such, using inversions can add interest to an otherwise dull I-V pattern.
Another use for bass instruments is pedal-point. This is done by sustaining the tonic or fifth of a key while the rest of the instruments go to another chord. When used repetitively, it can create tension that demands a final resolution.