What is meant by trumpet compression and how is it tested?

What we mean is that the valves have good compression. A very simple test that you can do is to pull out one of your valve slides, after it is out, depress the piston. You should hear a "pop", if this is done before the air in the slide has equalized on it's own. In many instances, older trumpets can lose their valve compression due to normal wear of the valves and/or the valve casings. High quality brass repair shops actually have a machine that their specialists can use to measure the exact compression of each piston.

Depending upon the severity of the wear, a thicker viscosity valve oil can be used to make the valves more efficient. Hetman is a company that offers piston oils with 3 different viscosities. Trumpets that are built with very tight "tolerances" can use their #1 formula. The #2 formula works well for most trumpets, and the #3 is actually designed to be used on trumpets that have some wear.

Eventually, if the compression becomes very bad, the valves can be rebuilt and hand-lapped to a "like new" tolerance. This is not an inexpensive repair option, so it should be done on a trumpet that you value, and intend to keep playing for a very long time.

Depending upon the types of materials used for building the pistons, or the machining tolerances for each valve, this "compression" does vary from manufacturer to manufacturer.

In my opinion, a trumpet that has very tight valve tolerances, or compression, "can" lack flexibility, as tighter compression yields tighter note "slotting". What it really comes down to is resistance. We all need to find a trumpet that has a resistance that matches our playing style and needs. Because there are many very well built trumpets available in today's market, it is possible for us to find a high quality trumpet without it having to be the same name brand.

As you can see, the subject of compression has an effect on the entire

trumpet. To give a simple answer to the question really doesn't take all of the other things that are affected into account.

Best of luck to you!

I'm not exactly sure but it seems to me that it will have something to do with tone quality.

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