Electric bassists play the bass guitar. In most rock, pop, metal and country genres, the bass line outlines the harmony of the music being performed, while simultaneously indicating the rhythmic pulse. In addition, there are many different standard bass line types for different genres and types of song (e.g. blues ballad, fast swing, etc.). Bass lines often emphasize the root, third, and fifth of the chord progression being used in a given song. In addition, pedal tones (repeated or sustained single notes), ostinatos, and bass riffs are also used as bass lines. While most electric bass players rarely play chords (two or more notes all sounded at the same time), chords are used in some styles, especially jazz, progressive rock or heavy metal, and country.