Throughout their career, the band's style has remained largely unchanged, in spite of the addition of guitar synthesisers on 1986's "Somewhere in Time", keyboards on 1988's "Seventh Son of a Seventh Son", and an attempt to return to the "stripped down" production of their earlier material on "No Prayer for the Dying". In recent years, however, the band have begun using more progressive elements in their songs, which Steve Harris describes as not progressive "in the modern sense, but like Dream Theater, more in a 70s way". According to Harris, "Seventh Son of a Seventh Son" was the band's first album which was "more progressive", while they would only return to this style from 1995's "The X Factor", which he states is "like an extension of "Seventh Son"..., in the sense of the progressive element to it". The development contrasts with the band's raw-sounding earlier material, which AllMusic states was "clearly drawing from elements of punk rock", although Harris firmly denies this.