Instrument
A tool for tone production.
What it means
A musical instrument is a device that is built or used to bring forth notes and sounds. The usual classification orders instruments by what vibrates in them: idiophones, in which the body of the instrument itself sounds; membranophones with a vibrating head; chordophones with strings; aerophones with an air column; to these are added electrophones, in which the sound is produced or substantially shaped electronically. The human voice is usually considered separately, although it works on the same principle as a wind instrument with vibrating lips.
Musical use
Every instrument brings with it properties that shape the music written for it: range, volume range, response, agility, the ability for polyphony, and the question whether a note can be sustained or decays of itself. A harpsichord demands a different way of writing from a grand piano, a trumpet a different one from a violin. Composers therefore think not only in notes but in instruments; the art of instrumentation consists in assigning musical ideas to the sounding bodies that carry them best. Conversely, technical innovations — valves, key systems, the cast-iron frame of the piano — have changed music itself.
Performance practice
Get to know your instrument as a sounding body, not only as a fingering system: which registers respond easily, which notes are tricky, how the colour changes over the range. This knowledge eases fingerings, breathing places, and planning of volume more than any general rule. Keep the instrument in good condition; a large part of supposedly playing difficulties has mechanical causes. Protect it from fluctuations of temperature and humidity, because wood, metal, and leather react differently to them. Have maintenance work carried out professionally and document repairs.
Remember that instruments have changed historically: a violin of the eighteenth century is set up differently from a present-day one, a clarinet had fewer keys, a piano a lighter touch. Whoever plays older music should know what it was written for, even if they play it on a modern instrument. With scoring indications, check which instrument is actually meant, since names migrate.