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What Is The “Bore” On A Trumpet? (Explained For Beginners)

If you look at a trumpet, you’ll notice that it’s made up of brass tubes.

All brass instruments have a similar construction, with one key difference: bore size.

Let’s discuss what a bore is on a trumpet and why you need to know about it:

Here’s an Idea of What a Bore is:

Brass instruments are comprised of brass tubing. The bore is the internal diameter of these tubes. For trumpets, smaller bores will produce a mellow, soft sound but have a limited range. Larger bores have a bright, aggressive tone but need much more airflow.

How to Find Out the Size of Your Bore:

If you don’t know the bore size of your trumpet, you can easily find out.

Especially if you are selling your trumpet, you’ll need to list the bore size so that buyers gain correct information about your instrument.

The manufacturer may list the bore size on its website. You can search for your trumpet’s make and model, and it’ll be listed along with other specifications.

For pre-owned instruments, you can probably figure out the bore in the same way. As long as you know the serial number, you can search for the information on its manufacturer’s website.

If you don’t know the model or serial number, you may measure the bore yourself. Luckily, this is a straightforward process.

Manufacturers generally measure the bore size using the valve casing on the second valve. You can remove your trumpet’s valves and valve casings and find the area where the second valve fits into the valve casing. This will be halfway up your middle valve.

This valve slide is what you’ll need to measure. Most manufacturers use this area to determine bore size. Plastic calipers are a great tool for this process.

Remove the second valve slide, placing the smaller jaws of the caliper into one side of the tubing. Then open the jaws until they align with the sides of the valve slide. They should be firmly against the sides, so open them until they can’t widen any further.

Read the measurement on the caliper. This will tell you the exact bore size. You may want to do this a couple of times to ensure that you measured correctly.

What is the Most Common Bore on a Trumpet?

Every brass instrument has a specific bore size.

You’ll be able to notice this by looking at each instrument.

Larger instruments, like tubas, will have a much wider diameter in their tubing. Trumpets have a smaller bore size, so they’ll have narrower tubes.

There are three different bore sizes for trumpets:

  • Medium bore
  • Medium-large bore
  • Large bore

For trumpets with a smaller bore size, players will need less breath to make a note. This makes these instruments much easier to play.

The timbre will also change, being richer with a controlled tone.

The most common trumpet is a Bb trumpet. Their bore size could range from .459 to .468 inches.

Beginner student trumpets usually have a medium-large bore which tends to have a bore of .459 inches. Because they don’t have a large bore, they are easier to play. Students don’t have to produce a lot of air to play.

For intermediate and professional players, trumpets with a larger bore are more common. Experienced players have the air capacity to find success with these instruments.

Larger bores generally have a wider, broader sound. Some players prefer this tone, but this is a common debate among trumpet players.

Advanced players choose their instruments based on personal preference.

What is the Biggest and Smallest Bore?

The bore sizes for trumpet range from .459 inches to .468 inches.

They are generally categorized as medium, medium-large, or large bore.

Piccolo trumpets have the smallest bore. At .445 inches, they are the smallest brass instrument.

For other brass instruments, the bore size will vary. French horns will be between .468 and .472 inches.

A large-bore trombone typically has a bore of .547 inches. Euphoniums are close to this, being from .570 to .660 inches.

Tubas will have the largest bore. This is around .750 inches.

How Do the Different Bores Affect the Sound?

Bore size is all about the width of tubing.

For brass instruments, this is very important in creating a specific sound. Different bores will affect the way an instrument sounds.

A smaller bore will have a more mellow tone. With a small bore size of around .450 inches, your trumpet will sound softer.

Smaller bores are not very popular. They can often be restrictive to a player. A smaller bore will limit the range of a trumpet player.

A bigger bore will have a brighter tone. A trumpet with a large bore size will sound aggressive, with a wider tone.

Trumpet players often find it harder to play with a larger bore because it requires much more air.

Beginner trumpet players will choose an instrument with a medium bore. With a bore that isn’t too large or too small, they can easily produce notes.

If you are a new trumpet player, you want to avoid large bores. You will likely become frustrated because it needs so much airflow to produce any notes.

What Bore Do Professional Trumpeters Use?

With more experience, players might choose an instrument with a larger bore.

Even though this requires airflow, it is great for live performances, large venues, outdoor events, and playing first-chair solos.

Both intermediate and professional players frequently have trumpets with larger bores. With these instruments, they can make a thunderous, flamboyant tone that easily impresses audiences.

However, medium-large bores are also a popular choice. It depends on the personal preference of each trumpet player.

Some trumpeters favor a mellower, rich timbre instead.

Can You Change the Bore on Your Trumpet?

There’s no way to alter the bore size of your instrument.

When you purchase a new trumpet, make sure that you know which bore you are getting.

Each player has a different embouchure, lip aperture, and air control. What works for someone else might not work for you.

It is best to start with a medium-large bore when beginning to play trumpet for the first time. This will give you a nice introduction to the trumpet without the added difficulties of small and large bores.

Once you have some experience, you can venture onto different bores. You can try them out at various music stores or borrow your friend’s trumpet.

Play on as many different instruments as you can before buying a new instrument.

You can’t change the bore of an instrument, so some professionals have multiple trumpets. They might have small and large bore trumpets to play different types of music.

Since each has a specific timbre, they can be valuable in different ways.

Final Thoughts

Trumpets usually have a bore size of .459 inches to .468 inches.

These are referred to as medium, medium-large, and large bores.

Beginners should purchase a trumpet with a medium-large bore. This will be fairly easy to play with a normal range. With smaller or larger bores, this changes.

Smaller bores need much less air to make notes. They have more air resistance but have a more limited range. Larger bores have a distinctive, bright tone but have less air resistance.

Because of this, players need to circulate large amounts of air to play any notes.

A trumpet’s bore is largely a matter of preference. Each player will favor either small or large bores.

Sometimes, professional players play both. They realize that each bore size is ideal for a specific composition or performance.


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