The experimentation evident on "Somewhere in Time" continued on their next album, entitled "Seventh Son of a Seventh Son", which was released in 1988. A concept album, based on the 1987 novel "Seventh Son" by Orson Scott Card, would be the band's first record to include keyboards, performed by Harris and Smith, as opposed to guitar synthesisers on the previous release. After his contributions were not used for "Somewhere in Time", Dickinson's enthusiasm was renewed as his ideas were accepted for this album. Another popular release, it became Iron Maiden's second album to hit No. 1 in the UK charts, although it only achieved a Gold certification in the US, in contrast to its four predecessors.