Tubas begin their lives as small euphoniums, but quickly move up in rank to a full fledged tuba. They feed on notes in the middle of the staff, and progress downwards as they age. The diagram below provides more information.
The Endangered Tuba
The Tuba is one of the largest brass instruments in the world, with an adult male reaching upwards of 4 feet in height and 60 lbs in weight. Tubas are an endangered species, because most have been beaten to death by the "Horn Denters". There are now believed to be less than 10000 tubas left in the world. The Horn Denters usually join band because their parents forced them to. Thus they are very angry fellows and like to take out their anger on tubas. If a tuba is strong enough to survive this ordeal and eats enough pedal tones, then it will go on to become a 6/4 adult tuba. They survive in band rooms, concert halls, and are sometimes lucky enough to gain a "tuba player", who will help the tuba thrive and teach them how to sing.
The Poison Tuba
Although they are not considered to be poisonous, the saliva from a Tuba contains deadly bacteria. This saliva is so toxic, that 0.006 mg of its venom will kill a flute. The spit is initially very painful due to its acidity. The patient will immediately feel tingling around the mouth and tongue, facial muscle twitching, nausea, vomiting, profuse sweating, salivation, and shortness of breath. Patients may rapidly develop agitation, confusion and coma associated with hypertension, metabolic acidosis, dilation of the pupils, and generalised muscle twitching. Death results within the hour from progressive hypotension or possibly raised intracranial pressure resulting from cerebral oedema.
The Three Valve Tuba
An F and Eb tuba can only gain valves by finding the valve tree. The sacred Valve-Tree can only be found in the center of the black forest. This forest is guarded by several grand pianos, and one master piano called the Bösendorfer. To reach the sacred Valve Tree the tuba must sneak into the Black Forest and discretely make its way through the underbrush. If a piano hears the tuba, it will be tortured with a barrage of C7's. If the tuba can fight off the pain they it may try to light the piano on fire with its valve oil or, if it a particularly tough tuba, scare off the piano with a barrage of pedal tones. Once the tuba reaches the Valve-Tree it must face off against the Imperial Grand, the Bösendorfer. The fight has never been seen by humans, as the tuba and piano move too fast, but it is generally understood that the Bösendorfer will let the tuba pass if it is worthy. The tuba then heads down a small dirt path and reaches a tree that has valves just like a cherry tree has cherries. The tuba steps under the golden valves and faces up. Immediately there is a blinding flash of light and the Tank Fanfare is heard ringing across the forest. If you listen closely enough, you may hear the newly valved tuba playing the melody. The tuba is then escorted out of the forest by several pianos, and is sent off on its own. The tuba will no longer be bothered by the horn-denters, and will be respected by the other brass instruments for the rest of its life.