Most brass players believe that the playing qualities of their instruments are affected by the method of construction and the materials used. Composition, thickness, and hardness of the metals used are all cited as important. Phrases such as ``hand-hammered bell'' are often found in advertising literature. This paper will give an overview of the tools, techniques, and materials used by brass-instrument makers today and in centuries gone by. Traditional techniques are still used along with the latest metalworking methods, so that a present-day instrument may contain some parts produced by computer-controlled machine tools and others made using processes familiar to 16th-century artisans. Players' ``lore'' will be compared with available experimental data. It is likely that more questions will be raised than answered.