The 6ths is a term used in music theory to describe intervals that span six diatonic scale degrees. For example, in the C major scale, the interval from C to A is a sixth. There are two main types of sixths: major and minor. A major sixth has a larger interval, while a minor sixth is smaller. In addition to their use in melodies, sixths are also important in harmony. They can create rich, pleasing sounds when used in chords. Musicians often use sixths to add depth and emotion to their compositions, making them a fundamental aspect of music creation.