How do you play double b flat on tuba?

To play a double B-flat on the tuba, which is the lowest note in the standard tuba range, you should first ensure your instrument is properly tuned. Use your lips to create a firm yet relaxed embouchure, and take a deep breath to support your sound. Then, press down the appropriate combination of valves—typically the first and third valves—to produce the note. Finally, use your air support to maintain a steady tone, focusing on producing a clear and resonant sound.