Parts of a Trombone: Labeled Diagram and What Each Part Does

Knowing the names of the parts makes the first months of band much easier. A band director will say things like "lock your slide," "put a little slide cream on your inner slide," or "empty your water key." This guide walks along the trombone the same way the air does, from the mouthpiece to the bell, and explains what each part does and why it matters to the way your trombone plays.

The mouthpiece

• Mouthpiece. The removable metal cup you press your lips against. It has a rounded rim that rests on your lips, a cup where your lips buzz, and a shank that slides into the trombone. A trombone mouthpiece is larger than a trumpet mouthpiece, which helps it play lower notes. Many beginners start on a 12C. Trombones come with either a small or a large shank opening, so a new mouthpiece has to match.
• Mouthpiece receiver. The short, thicker tube at the top of the slide where the mouthpiece goes in. Push the mouthpiece in with a gentle twist. Never tap or hit it in, or it can get stuck.

The slide section

• Inner slide. Two long, straight, polished tubes that stay still. One carries the mouthpiece receiver; the other connects to the bell section. You can see them shine silver when the slide is pushed out. The last few inches of each tube, called the stockings, are a touch wider, so the slide rides on a small area and moves easily.
• Outer slide. The long U-shaped part that fits over the inner slide and moves in and out. This is the part you play with. It has to be perfectly straight to glide; even a small dent can make it stick.
• Inner slide brace. The crossbar joining the two inner slide tubes, near the mouthpiece. Your left hand holds it, along with the bell brace, to carry the trombone's weight.
• Outer slide brace. The crossbar on the outer slide. Your right hand holds it lightly to move the slide.
• Slide lock. A small turning collar near the top of the slide. When it is locked, the outer slide cannot slip off. Lock it every time you stop playing, carry the trombone or put it together.
• Slide crook. The rounded bend at the far end of the outer slide, where the air turns around. Many trombones have a small rubber bumper on the end to protect it if it touches the floor.
• Water key. Also called the spit valve. A small lever on the slide crook. The warm air you blow turns to water inside the cool tubing (it is mostly condensation, not spit), and it runs down into the crook. When the trombone starts to sound gurgly, press the water key and blow gently to push it out.

The bell section

• Bell section. The second main piece: the bell, the long tube that leads to it, and the loop at the back. It rests on your left shoulder when you play.
• Bell lock nut. The threaded ring that joins the bell section to the slide section. Hand-tighten it until it is snug; never force it.
• Bell brace. The bar between the bell tube and the tube that leads back toward the slide. Your left thumb wraps around it, so it helps you hold the trombone steady.
• Tuning slide. The large U-shaped loop at the back of the bell section. Pulling it out makes the trombone slightly longer and lower in pitch; pushing it in raises the pitch. This is how you tune to the band. It stays put while you play.
• Tuning slide brace. The bar across the tuning slide that keeps its two tubes the right distance apart.
• Bell. The wide, flared end. It lets the sound out and sends it toward the audience. A larger bell gives a darker, broader tone.
• Bell rim. The rolled edge around the end of the bell. It stiffens the thin metal and protects it.
• Counterweight. Some trombones have a small brass weight near the back, usually on or near the tuning slide. It balances the weight of the bell and slide out in front, so the trombone feels lighter in the left hand. Many student trombones do not have one, and they play just as well without it.

How a trombone makes its sound

A trombone has no reed and no strings. The sound starts with your lips. You press them lightly together inside the mouthpiece and blow, so they vibrate very quickly. Brass players call this a buzz. The buzz makes the column of air inside the tubing vibrate, and the tubing and bell turn it into a full, warm note.

The same length of tube can play several notes without moving the slide. Tighter lips and faster air give a higher note; looser lips and slower air give a lower one. These natural notes are called partials. Moving between them with your lips is a big part of learning any brass instrument.

A tenor trombone has roughly twice as much tubing as a trumpet. That is why it plays about one octave lower.

How the slide changes the notes

A trumpet uses three valves to add extra tubing. A trombone does the same job with its slide. Pushing the slide out makes the tube longer, and a longer tube plays a lower note. Because the slide moves smoothly, a trombone can also glide from one note to the next, which is the famous trombone "slide" sound.

There are seven slide positions:

• 1st position is the slide all the way in, resting gently near the slide lock.
• Each position further out lowers the note by one half step.
• 7th position is near the end of the slide, with your arm almost fully stretched. Younger players with shorter arms sometimes need a little help reaching it at first.

The positions are not marked on the slide, and they get a little farther apart as you go out. On most tenor trombones, 3rd position is a little before the bell and 4th position is just past it. Those are only landmarks; your ears and your teacher help you find the exact spot.

Each position can play several notes, chosen by your lips and air. For example, 1st position plays Bb, F, the higher Bb and D, all with the slide in the same place.

What an F attachment is

Some trombones, often called Bb/F trombones or trombones with an F attachment, have an extra loop of tubing and a valve worked by a trigger under the left thumb. Pressing the trigger sends the air through that extra loop and lowers every note by a fourth. That lets you play low notes that normally need the slide far out, such as C in 6th position, much closer in. It also adds some low notes a straight trombone cannot reach. Most players start on a straight Bb tenor trombone and move to an F attachment as they advance.

Trombone music and pitch

The tenor trombone is built in Bb, but in school band and orchestra it reads music in bass clef at concert pitch. A written C sounds as a C, the same note a piano plays. That makes it easy to play alongside piano, guitar or bass from the same music.

How to hold a trombone

Your left hand holds the weight. Wrap your left thumb around the bell brace (or rest it on the trigger on an F attachment trombone), rest your index finger on the mouthpiece receiver, and wrap your other fingers around the inner slide brace. Your right hand moves the slide. Hold the outer slide brace lightly between your thumb and first two fingers, keep your wrist loose, and let the slide do the work.

Basic trombone care

• Keep the slide smooth. Wipe the inner slide clean, then put a thin layer of slide cream on the stockings and mist it with a little water from a small spray bottle, or use a few drops of slide oil. Work the slide in and out. A smooth slide makes everything easier.
• Lock the slide. Every time you stop playing, lock the slide. A slide that falls off and hits the floor almost always needs a repair.
• Protect the slide. When you are not playing, the trombone goes in its case or on a trombone stand. Never lean it against a chair or a wall, where it can fall.
• Grease the tuning slide. A little tuning slide grease keeps it moving and airtight. If you have an F attachment, a drop of rotor oil now and then keeps the valve quick.
• Empty the water. Open the water key whenever the sound gets gurgly, and before you put the trombone away.
• Clean the mouthpiece. Rinse it in warm water and run a mouthpiece brush through it about once a week.
• Give it a bath. Every month or two, wash the bell section and slide in lukewarm water with a little mild dish soap and run a flexible cleaning snake through the tubes. Be gentle with the slide, rinse, dry, then put fresh slide cream on. Use lukewarm, not hot, water, which can harm the lacquer.
• Stuck mouthpiece or sticky slide? Do not use pliers or force the slide. A repair shop can pull a mouthpiece in a minute and straighten a slide properly.

Most of these supplies come together in a brass care kit; see our brass accessories.

Trombones to learn the parts on

Every trombone below has the parts described in this guide, and each comes with a case. Prices and stock update automatically.

See every model in our trombones section. If your child is still choosing an instrument, the school band instrument guide compares the band instruments side by side. Curious about the trumpet? See the parts of a trumpet and our beginner trumpet buying guide.

Frequently asked questions

What are the main parts of a trombone?

The mouthpiece, the slide section (inner slide, outer slide, slide crook and water key) and the bell section (bell, tuning slide and bell brace). The slide section and bell section screw together with the bell lock nut.

How many positions are on a trombone slide?

Seven. 1st position is the slide all the way in, and each position further out lowers the note by a half step, down to 7th position near the end of the slide. Each position can play several notes, chosen with the lips.

What is the difference between the inner slide and the outer slide?

The inner slide is the pair of straight tubes that stay still; one holds the mouthpiece. The outer slide is the U-shaped part that fits over them and moves in and out when you play.

What is the slide lock on a trombone for?

It holds the outer slide in 1st position so it cannot slip off. Lock it whenever you are not playing, and especially when you put the trombone together or carry it.

What does the trigger on a trombone do?

On a trombone with an F attachment, the trigger under the left thumb opens a valve that sends the air through an extra loop of tubing. It lowers the note by a fourth, which makes some low notes easier and adds a few that a straight trombone cannot play.

Does a trombone have valves?

A standard tenor trombone does not; it uses the slide. A valve trombone has three piston valves instead of a slide and uses the same fingerings as a trumpet or baritone.