A tuning system is a method used to determine the pitch relationships between notes in music. The most common system is the equal temperament, where the octave is divided into 12 equal parts, allowing instruments to play in any key without sounding out of tune. This system is widely used in Western music. Other tuning systems include just intonation, which is based on simple frequency ratios, and Pythagorean tuning, which emphasizes perfect fifths. Each system offers unique characteristics and can influence the overall sound and harmony of music, making them important for composers and musicians.