In music an interval is the distance in pitch between two notes, counted from the lower note upwards, with the lower note as the first of the interval. The violin, for example, is tuned in intervals of a fifth, G to D, D to A and A to E, the double bass in fourths, from E to A, A to D and D to G. Harmonic intervals occur simultaneously, as when a violinist tunes the instrument, listening carefully to the sound of two adjacent strings played together. Melodic intervals occur between two notes played one after the other.