Parts of a Tuba – Mouthpiece, Valves, Slides and Bell

All 18 parts on the diagram

Show the list

Tubing and bell 3

Leadpipe The first tube. The mouthpiece fits into its end.
Bell The wide flared end of the tube, where the sound leaves.
Bottom bow The large U-shaped bend that joins the bell to the rest.

Valves and slides 8

Valves Pressing a valve sends the air through an extra loop of tubing.
Main tuning slide Moving it in or out tunes the whole instrument.
Valve buttons The fingers press these to push the pistons down.
Valve caps Screw caps on the casings. Undone, they let the pistons out.
Valve casings Each piston moves up and down inside its own casing.
Valve slides A loop for each valve. The third lowers the pitch most.
Water key Pressing it drains water that collects from the player's breath.
Thumb ring The right thumb hooks into it to steady the hand.

Mouthpiece 7

Mouthpiece The player's lips buzz against it to start the sound.
Receiver The socket on the leadpipe that the mouthpiece fits into.
Rim The rounded edge that supports the player's lips.
Cup The bowl-shaped hollow. The throat is at its base.
Throat The narrowest opening, at the base of the cup.
Backbore The channel that runs through the shank.
Shank The stem of the mouthpiece. It fits into the receiver.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it for this part. (1) Wikipedia, text only: Tuba (leadpipe and its receiver, piston and rotary valves, top-action pistons and their buttons, valve slides, thumb ring, the mouthpiece with its cup, throat, backbore and shank, the usual number of valves), https://en.wikipedia.org/wiki/Tuba ; Brass instrument (main tuning slide, valve slides, what each valve does), https://en.wikipedia.org/wiki/Brass_instrument ; Brass instrument valve (piston, casing), https://en.wikipedia.org/wiki/Brass_instrument_valve ; Water key, https://en.wikipedia.org/wiki/Water_key ; Leadpipe, https://en.wikipedia.org/wiki/Leadpipe ; Mouthpiece (brass) (rim, cup, throat, backbore, shank), https://en.wikipedia.org/wiki/Mouthpiece_(brass) . (2) An instrument maker's online Musical Instrument Guide, The Structure of the Tuba (its part list: bell, slides, valves, mouthpiece, main tuning slide, water key; top-action, front-action and rotary tubas; what each valve lowers), https://www.yamaha.com/en/musical_instrument_guide/tuba/mechanism/ . (3) Clifford Bevan, The Tuba Family (1978), searched in full text at https://archive.org/details/tubafamily0000beva_y3y3 (its labeled figures: bell, mouthpipe, mouthpiece, bottom bow, water-key, valve casing, valve top cap, valve-slides; mouthpiece rim, cup, throat, backbore, shank; the thumb-ring for the right thumb). (4) Clayton H. Tiede, The Practical Band Instrument Repair Manual (1970), searched in full text at https://archive.org/details/practicalbandins00tied (mouthpipe, mouthpiece receiver, valve caps, valve casing, valve button, valve slides, main tuning slide, water key or spit valve, shank, rim). (5) The Tuba Source Book (1996), searched in full text at https://archive.org/details/tubasourcebook0000unse (bottom bow, leadpipe, main tuning slide, piston valves, valve slides, backbore, cup, throat, rim). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's instrument, nothing traced. Licence: own work

How it works

A tuba is one long tube that widens from the mouthpiece to the bell. Follow the breath: mouthpiece, leadpipe, valves and slides, the big bottom bow, then out of the bell.

Read the full guide

Three views, mouthpiece to bell

Numbers 1 to 6 are the whole tuba. Numbers 7 to 13 are the valves close up: buttons, caps, casings and slides, with the water key, the thumb ring and the receiver. Numbers 14 to 18 are inside the mouthpiece.

What the valves do

Pressing a valve sends the air through its slide, an extra loop of tubing, so the note drops. The first valve lowers it a tone, the second a semitone and the third a tone and a half. This is a top-action tuba with three pistons; others have rotary valves worked by levers.

Water from the player's breath collects at the low bends of the tubing. Pressing the water key lets it drain.

Questions and answers

What are the main parts of a tuba?

The mouthpiece, the leadpipe, the valves with their slides, the main tuning slide, the large bows of tubing and the bell. Smaller parts include the water key, the valve caps and the thumb ring.

How many valves does a tuba have?

Usually four or five, although some models have three or six. Smaller student tubas often have only three.

What is the water key on a tuba for?

It is a small sprung valve at a low bend of the tubing. Pressing it drains the water that condenses from the player's breath, so the instrument does not have to be turned over.

What are the parts of a tuba mouthpiece?

The rim, which supports the lips; the cup, a bowl-shaped hollow; the throat, the narrow opening at its base; and the backbore, the channel through the shank. The shank fits into the receiver on the leadpipe.