The 1950s saw the emergence of free jazz, which explored playing without regular meter, beat and formal structures, and in the mid-1950s, hard bop emerged, which introduced influences from rhythm and blues, gospel, and blues, especially in the saxophone and piano playing.
The first heavy metal bands such as Led Zeppelin, Black Sabbath and Deep Purple attracted large audiences, though they were often derided by critics, a status common throughout the history of the genre. During the mid-1970s, Judas Priest helped spur the genre's evolution by discarding much of its blues influence; Motörhead introduced a punk rock sensibility and an increasing emphasis on speed.
The first third of the 19th century saw the high point of the bel canto style, with Rossini, Donizetti and Bellini all creating works that are still performed in the 2000s It also saw the advent of Grand Opera typified by the works of Auber and Meyerbeer.
Grunge lyrics are typically angst-filled, and anguished, often addressing themes such as social alienation, apathy, confinement, and a desire for freedom. A number of factors influenced the focus on such subject matter.