1. Lines drawn perpendicularly across the staff to divide it into measures. The term also means measure in common usage, but the bar is strictly the line itself, and not the measure it defines. The bar came into use in music after 1600.
2. A strip of metal or wood that is used to sound a specific pitch when struck with a mallet. Bars are found on mallet percussion instruments such as orchestra bells, glockenspiel, marimba and xylophone.