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Every Mechanism

Home How a Trombone Works

Tenor trombone in B♭ · a guided tour

How a trombone works

No valves. No keys. Just buzzing lips, 2.7 metres of brass tubing, and a slide that changes how long that tubing is.

Take it apart
2.74 m
of tubing, about 9 ft
7
slide positions
0
valves or keys
58 Hz
lowest pedal, B♭1
A lacquered brass tenor trombone seen from the bell end, slide stretching away to the right.

Video

How a Trombone Works - Why Sliding Changes the Note

Watch on YouTube

3D model · 360° · zoom

Pick it up and play

Drag to turn it any way, scroll or pinch to zoom, right-drag to move it. Grab the gold slide and pull it, or click a part to see what it does.

Try itGrab the slide and pull. Click the mouthpiece, the bell, the tuning slide, the water key or the slide lock.
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Lips
Scroll to take it apart

Three pieces and a slide

Keep scrolling: the model comes apart in the same order a player packs it away.

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  1. Step 1Pull the mouthpieceIt sits in a tapered socket. A gentle twist frees it.
  2. Step 2Loosen the bell nutA knurled collar screws the bell section onto the slide.
  3. Step 3Lift off the bellBell, tuning slide and neckpipe come away together.
  4. Step 4Glide off the slideUnhook the lock and the outer slide rides off the inner one.
Meet the parts

Twelve parts, one long tube

Tap any part of the model or pick a name below. It is all one continuous tube of air, from your lips to the bell, plus the hardware that holds it together.

The trombone taken apart: bell section above, mouthpiece at left, inner and outer slide below.

Hover or tap the model. Gold rings mark every part.

Parts diagram

Every part, labelled

Numbers 1 to 11 follow the air from your lips to the bell. Numbers 12 to 16 are the hardware that holds it all together.

Side view of a tenor trombone with sixteen numbered parts.
    Where the sound starts

    It starts with a buzz

    A trombone has no reed and no string. The player’s lips do the vibrating, buzzing against the mouthpiece rim like a very fast, very controlled raspberry.

    The mouthpiece sawn in half lengthwise, seated in the receiver. The cut faces are shown in red.

    The model’s mouthpiece, sawn in half and seated in the receiver. Air flows left to right.

    Each time the lips open, a puff of air pushes a pressure pulse into the tube. It races to the bell at the speed of sound, about 343 metres a second, and much of it bounces back from the flare.

    The round trip takes about 16 thousandths of a second. When the echo reaches the mouthpiece it nudges the lips at just the right moment, so lips and air settle into step. The buzz becomes one steady note, and the tube, not the lips, sets the pitch.

    Slowed down about 250 times. Press a button to hear the difference.
    The air inside

    A standing wave, nine feet long

    X-ray view of the trombone model with the air column shown as coloured particles: red and blue bands along the tubing.
    X-ray view of the model. Every dot is a parcel of air. Red means pressure above normal and blue below. Pale stretches are nodes, where the pressure hardly changes.

    Only certain wave shapes fit between the lips and the bell. Each one is called a partial. At the lips the pressure swings hard; at the bell it hardly swings at all, because there the air spills out into the room.

    Tighten the lips and the buzz jumps up to the next shape, with one more quiet node inside. In first position the partials are B♭2, F3, B♭3, D4, F4 and up: the notes of a bugle call.

    A plain tube closed at one end would only give every other note of that series. The bell’s flare and the mouthpiece nudge the resonances until they line up with 2, 3, 4, 5, 6 × one base frequency. That is what makes the trombone sound so musical.

    higher pressure lower pressure node
    Play the slide

    Seven positions, one semitone apart

    Drag the slide or press 1 to 7. Pick a partial, the way a player tightens their lips. Press Play and keep dragging for a glissando.

    Side view of the trombone: bell section, inner slide and mouthpiece.
    The outer slide.

    Drag the gold slide down ↓

    B♭3note
    1position
    0.0slide out, cm
    2.74tube, m
    233frequency, Hz
    Keys: 1–7 positions · ↑ ↓ partials · hold Space to play
    Partial · lip tension

    Why the positions spread out

    Each semitone lower needs about 6% more tubing than the note before, so every step reaches a little further than the last: 8.1 cm from 1st to 2nd position, but 10.9 cm from 6th to 7th. And because the slide has two legs, every centimetre of travel adds two centimetres of tube.

    Looking straight into the flared brass bell.
    The bell

    Where the sound gets out

    Inside the tube, sound bounces back and forth. The flared bell is a gradual doorway: low notes mostly reflect and keep the standing wave going, while enough sound escapes to fill a concert hall.

    The flare also tunes the resonances into the neat series you heard above. High notes beam straight ahead, so a trombone sounds brighter when it points right at you.

    Straight muteA cone in the bell: bright, metallic, a little nasal.
    Cup muteAdds a cup over the cone: soft, round, far away.
    Harmon muteAir forced through a small tube: buzzy and thin.
    PlungerYes, a sink plunger. Open and close it for “wah-wah”.
    More to know

    The family, the history, the care

    Trombone family, by length of tubing

    Lengths are for the plain slide in 1st position, scaled from the tenor’s 2.74 m by pitch. Dashed: extra tubing a valve can switch in. A contrabass in B♭ runs to about 5.5 m.

    Five centuries of slide

    1. The sackbut appears in Europe, one of the first instruments with a telescopic slide.
    2. Monteverdi uses trombones to paint the underworld in his opera L’Orfeo.
    3. Mozart gives the tenor trombone a famous solo in the Tuba mirum of his Requiem.
    4. Beethoven brings trombones into the symphony for the blazing finale of his Fifth.
    5. New Orleans “tailgate” players such as Kid Ory make the glissando a jazz signature.
    6. J. J. Johnson plays bebop at full speed and proves the slide can keep up.
    7. “Seventy-Six Trombones” marches onto Broadway in The Music Man.

    Looking after one

    • Lock the slide whenever you stop playing, so it can’t slip off and dent.
    • Keep the slide slick with slide cream or slide oil and a spritz of water. Wipe off the old film first.
    • Empty the water key often, especially in cold rooms.
    • Rest it on its bell or on a stand, never on the slide.
    • Give it a lukewarm bath now and then, and run a cleaning snake through the tubes.
    • Travel with it in its case. A tiny dent in the inner slide can stop the outer slide gliding.

    Things worth knowing

    “Big trumpet”That is what trombone means in Italian. The old English name, sackbut, comes from French words for pull and push.
    The built-in swoopBecause the slide moves smoothly, a trombone can glide from note to note in one unbroken sweep.
    Pedal notesBelow B♭2 sits a deep pedal B♭1 at about 58 Hz. The player’s lips and the higher resonances hold it up.
    Mostly not spitWhat drips from the water key is mainly condensation from warm breath on cool brass.
    Tuned by earThe seven positions are starting points. Players shift a few millimetres to fix the flat 5th and 7th partials.
    Wah-wahThe muffled voices of the grown-ups in the Peanuts TV specials were played on a muted trombone.
    Quick check

    Four questions