The boundaries between art and pop music became increasingly blurred throughout the second half of the 20th century. The first usage of the term "art rock", according to Merriam-Webster Online Dictionary, was in 1968. As pop music's dominant format transitioned from singles to albums, many rock bands created works that aspired to make grand artistic statements, where art rock would flourish. As it progressed in the late 1960s – in tandem with the development of progressive rock – art rock acquired notoriety alongside experimental rock.