There are three different types of rock music, alternative rock, classic rock, and hard rock, also known as metal. Alternative rock features a steady bass drum laying down the beat, with easy flowing guitar riffs over the top. The bass line is toned town, and the lyrics are sung with intensity an authority. Depending on the song, the guitars can either be acoustic guitars or electric guitars. Classic rock combines a steady driving bass drum sound, with high snare overtones, steady and often repeating guitar riffs, and an intensive bass line.