A Guide To The Different Parts Of A Trombone

Written by Dan Farrant
Last updated

Mechanically, the trombone is one of the simplest brass instruments. However, as with all musical instruments, there is a lot of technical jargon to learn that can be confusing at first. Learning what all the different parts of the trombone are will allow you to communicate effectively with your teacher and will help you when buying an instrument.  

In this article, we will look at the different parts of the trombone: what they’re called, how they work, and how they might differ from instrument to instrument.

Anatomy of a Trombone

Anatomy of a Trombone

The trombone is made up of three main components:

  • the bell section
  • the slide
  • the mouthpiece

These three components are regularly disassembled/assembled and are kept apart in the instrument’s case.

The slide is joined to the bell section by a threaded nut or collar and you have to make sure the threads line up so this connection is tight and the angle between the slide and bell section cannot change.

This angle should be 90o (right angle) or slightly less depending on the size of your hand and what is comfortable.

The mouthpiece is not fastened to the slide, it simply sits in the opening of the tube.

If you gently press the mouthpiece in it will not move around, however, be careful not to strike the mouthpiece as it can sometimes get stuck.

The Mouthpiece

Trombone Mouthpiece

We’ll start by looking at the Mouthpiece which is essentially a funnel and is the part of the instrument that you blow into.

Mouthpieces come in various sizes, and trombonists often have a few different ones that they use in different musical contexts.

However, as a beginner, it is often recommended that you don’t change your mouthpiece too often as it takes time to get used to any one model.

Sizes and Measurements

Mouthpieces come in a variety of different shapes and sizes each of which affects the way the mouthpiece feels to play and the sound it produces.

Generally, smaller mouthpieces make a brighter sound and make it easier to play higher.

Different manufacturers have different ways of labeling the measurements of a mouthpiece but to help explain here’s a handy guide.

Usually, a lower number correlates to a larger mouthpiece, but it is always worth checking the specifications.

Also, make sure to check that the size of the shank will fit in the bore size of your trombone.


Mouthpieces come in different materials but they tend to be made from brass, with either silver or gold plating.

Other metals, woods, and plastics can also be used for those with allergies; if you get particularly sore lips after playing, this is worth considering.

Non-conductive materials can also make playing in the cold easier.


Being essentially a long tube, the trombone’s Tubing is an important part that can determine the sounds produced.

The main thing to consider is the trombone’s bore size.

Bore Size

The trombone’s Bore Size is how we describe the diameter of the tubing.

Generally, it is consistent throughout the instrument apart from in two places which are the bell flare, where the tubing gets wider, and the mouthpiece which we covered earlier.

The exact measurements vary depending on the manufacturer, but you will commonly hear the terms large-bore and small-bore when discussing the size.

Large-bore trombones produce a darker, more orchestral sound, and small-bore trombones produce a brighter sound more suitable for jazz and pop playing.

Materials Used

The trombone’s tubing is generally made of lacquered brass, but you can occasionally find different materials in the bell section.

These different materials are largely cosmetic but may subtly change the tone and projection of the instrument.

Some people believe that lacquer (a thin protective layer) changes the tone of the trombone, although without this coating the brass will tarnish easily.

The Bell Section

The Bell Section amplifies and stabilizes the sound of the trombone.

For the tenor trombone in Bb, there are two main variations: the straight tenor trombone, and the tenor trombone with an F attachment.

The F attachment

The F attachment consists of a rotary valve, activated by a trigger, which allows the air to pass through an extra length of tubing coiled up in the bell section.

You press the trigger with your left-hand thumb, and this is connected to the rotary valve via string or a metal lever depending on the model.

The coiled length of tubing transposes the instrument down a perfect fourth into the key of F, hence its name.

The F attachment allows trombonists to avoid long positions and play some extra notes in the low register.

Other names for the F attachment include the plug or the valve.

The shape of the coiled tubing depends on the manufacturer, however, there are two general types:

  • an open wrap
  • a closed wrap

In the picture below, the open wrap is on the left, and the closed rap is on the right:

Open Wrap F Attachment

The Open Wrap F attachment has as few corners as possible, and this configuration increases the length of the instrument.

The open wrap creates a more open sound with less resistance (less force to blow against).

Closed Wrap F Attachment

The Closed Wrap F attachment is contained within the bell section; it has more corners and therefore a greater resistance.

Professional players use both configurations depending on the amount of resistance they like to play against.

The F attachment tuning slide changes the length of the extra tubing, meaning that you can sharpen or flatten these pitches individually.

Bass trombones have two sets of extra tubing, each with its own rotary valve and trigger.

We discuss the differences between both of these in more detail in our post about the different types of trombones here.

The Counter-Weight


Due to the trombone being very long, the Counterweight helps balance the instrument, so it isn’t too forward-heavy.

Often manufacturers will use the counterweight to display their logo.

If the trombone has an F attachment, this extra weight isn’t usually necessary and in this case, the manufacturer’s logo can usually be found engraved into the bell flare.

The Bell Flare

The Bell Flare

The Bell Flare is the part of a trombone that amplifies and stabilizes the sound.

The size of the bell depends on the model of the trombone and usually corresponds with bore size.

Alto trombones and small-bore tenor trombones will have a smaller bell flare, whereas large-bore trombones and bass trombones will have a larger bell flare.

Tuning Slides

The Tuning Slide is located at the top of the instrument and can change its pitch.

If you pull the slide-out, the instrument will sound flatter, if you push it in the trombone will sound sharper.

Bell Braces

The Bell Braces are the parts of the instrument that hold the trombone together securely.

On a straight tenor trombone, you will often wrap your thumb around the bell brace closest to your left hand.

The Slide

The Slide changes the pitch of the notes on the trombone; if you extend the slide then the pitch lowers, and if you contract the slide then the pitch rises.

Trombone slides are made up of two main parts:

  • the outer slide
  • the inner slide

The trombone slide is telescopic, which means that the outer slide is a tube that surrounds the inner slide (also a tube).

The Inner Slide is lubricated so that the outer slide can move up and down, changing the length of the tube overall.

A trombonist holds the 1st slide brace with their left hand, and this brace holds the inner slide in place.

They then move the outer slide with their right arm, holding the 2nd slide brace.

The slide is extremely delicate and must be in good condition for the instrument to play well.

If you are buying a trombone second-hand, the quality of the slide should be one of the first things you check.

The Stockings

The Stockings are located at the end of the inner slide.

They are hard to see, you are looking for a tiny ridge in the metal (an increase in the tube’s diameter).

This section of the inner slide makes constant contact with the outer slide, whereas the rest of the inner slide doesn’t fit as precisely.

The stockings reduce the friction on the slide by keeping the contact area small.

The Slide Lock

The slide lock is a small latch with stops the outer slide from moving.

This is a safety feature designed to make sure you don’t drop the outer slide when picking the instrument up.

You should always get in the habit of locking the slide when you are not playing, this reduces the likelihood of a costly accident!

The Bumper (Stopper)

The Bumper

The Bumper or Stopper is a small piece of rubber that is found on the very end of the slide that is a safety feature that protects the trombone.

It ensures that there are no hard collisions between the slide and the ground when the instrument is resting vertically on the floor.

It also improves friction with the ground, stopping the instrument from slipping away from you during bars rest (you will, unfortunately, come across these, time to time…)

The Water Key (Spit Valve)

You will be relieved to know that the water that comes out of the trombone is not actually spit, but condensation.

The Water Key, or ‘Spit Valve‘ as it’s also known, allows the condensation that builds up in the slide to escape.

When pressing the water key, hold the slide just lower than horizontal so that the lowest point is the water key hole to allow the water to escape out of the slide.

If you angle the slide downwards then the water will collect in the ‘u’ bend.

Summing up the Anatomy of the Trombone

In this article, we explored the three main components of the trombone in detail: the bell section, the slide, and the mouthpiece.

Hopefully, this information will make watching videos and talking to teachers easier!

When comparing instruments always remember to always try things for yourself.

Reading up specifications is a great starting point, but every instrument feels different to play and will change over time.

These nuances are what make musical instruments feel personal; never be afraid to try out older second-hand models, these are often sought-after by professionals!

Photo of author

Dan Farrant, the founder of Hello Music Theory, has been teaching music for over 15 years, helping hundreds of thousands of students unlock the joy of music. He graduated from The Royal Academy of Music in 2012 and then launched Hello Music Theory in 2014. He plays the guitar, piano, bass guitar and double bass and loves teaching music theory.