Timbre, sometimes called "color" or "tone color" is the quality or sound of a voice or instrument. Timbre is what makes a particular musical sound different from another, even when they have the same pitch and loudness. For example, a 440 Hz A note sounds different when it is played on oboe, piano, violin or electric guitar. Even if different players of the same instrument play the same note, their notes might sound different due to differences in instrumental technique (e.g., different embouchures), different types of accessories (e.g., mouthpieces for brass players, reeds for oboe and bassoon players) or strings made out of different materials for string players (e.g., gut strings versus steel strings). Even two instrumentalists playing the same note on the same instrument (one after the other) may sound different due to different ways of playing the instrument (e.g., two string players might hold the bow differently).