Progressive metal is a fusion between progressive rock and heavy metal. It is one of heavy metal’s more complex genres, due to its use of unusual and dynamic time signatures, long compositions, complex compositional structures, and skilled instrumental playing, where instrumental solos are detailed and extended. However, the latest age of Progressive Metal has favoured rougher lyrics and lower-pitched riff sequences with high amounts of strumming. Vocals, if present, are melodic (though there are a few that utilise unclean vocals), and lyrics are often philosophical, spiritual, or political. Many bands of the genre were influenced by the progressive rock band Rush, who would often incorporate elements of heavy metal into their music. Examples of the genre include Pain of Salvation, Queensrÿche, Dream Theater, and Fates Warning.