One of the nicest properties of music wire is that it is cheap and easy to find in almost any size. Sizes vary from about 0.002 inch diameters to about 1/2 inch diameter. The length of wire on a roll can be from 6 inches for some of the smaller diameters to 7 feet for some of the larger diameters. Sometimes it is sold by the pound (or ounce). It can be purchased in a wide variety of stores including hardware stores (usually the cheapest), art supply stores, general merchandising stores (Wal-Mart, Target), boating supply stores, hobby stores and scientific supply stores.
The property of malleability accounts for music wire's most common use: to make springs. If you bend music wire around a bar in loops, you have made a spring. Music wire tends to keep any shape you force it into, so springs made of music wire tend to last for a long time before they loose their shape. The ends can be shaped into hooks to make the stretch style springs (like those that keep screen doors closed), and the ends can be cut off to make compression springs (like those tiny springs in ball point pens). Some types of music wire need to be heated to hold new shapes, but most will hold a new shape that they have been forced into with tools, despite repeated use that involves gentle pushing and pulling.
Properties of music wire can vary slightly, which means people can use music wire for several different kinds of projects. If you want to restring your sitar, you should probably buy your music wire at a music store, but if you are using music wire to make jewelry, you should probably buy your music wire at an art store. The properties of music wire vary, depending on what the wire is made of and what it is coated with (if anything). Coatings are applied to music wire to prevent corrosion. Another factor that can affect the behavior of music wire is cross-sectional shape. Most music wire has a round cross-section, but it can also be flat or square in cross-section. The round cross-sectional wire is cheapest (easiest to manufacture) but the flat cross sectional wire makes better small springs. The square cross-sectional wire makes better pins to hold together small wooden items such as tiny boxes or the small furniture in dollhouses.