The trombone is an elegant, mellow-sounding musical instrument which is made up of a series of metal tubes. These tubes are used to control and alter the tone and timbre of the notes played through the instrument, but in order to make the instrument sound right, it needs to be made of the right materials. Mostly, trombones are made of brass, but there are a few other materials.
Bell and Flare
The bell and flare are made of thin pieces of brass sheet metal, shaped on a lathe into the two different pieces and soldered together into the trombone shape. The solder is made of a brass alloy, and the seam is often pressed together on a powerful machine. The assembly process usually bends the bell assembly out of shape, so it's placed on a wood or metal form and shaped with rollers before the flare is attached.
The tubing is brass as well, and is usually made from thicker brass tubes which are stretched and thinned. The tube is filled with water and frozen, before being bent into shape so the metal doesn't buckle. These tubes are then soldered together with plumbing solder and tools, into the standard trombone shape.
Braces and Locks
Thinner brass tubes are soldered onto the slide, bell, and tubing to give the instrument some structural integrity. Thicker sections of brass pipe are loosely screwed onto the slide to act as a slide lock mechanism.
Mouthpiece and Valves
Steel is another main metal used in making trombones, but it's not as ideal for making the sound as brass (which is used in a number of instruments in addition to trombones). The mouthpieces are often made of steel and titanium, although it's also possible to make them out of steel or gold. The valves, like the spit valve at the bottom of the slide, are also made out of steel because it's a sturdier material that's less likely to bend.