A musical interval is the distance between two notes in a piece of music. The term 'STEP' refers to a whole TONE, which is two semitones or one half of an OCTAVE. An OCTAVE is an interval of eight notes, and a semitone is the smallest interval in Western music. A tritone is an interval of three whole tones, and a REST is a period of silence in a piece of music. A fifth is an interval of five notes, and a sixth is an interval of six notes. A TONE is a whole STEP, which is two semitones, and a seventh is an interval of seven notes. An entr'acte is a short musical interlude between two acts of a play, and a whole STEP is an interval of nine notes.