Invented languages. Suicidal lighthouse keepers. Viking explorers. Chess games set to medieval folk music. Demis Roussos. Prog and outlandish concepts have always gone hand in hand. So we've delved into our record collections and unearthed a host of classics and curios. And we've made a Spotify playlist comprised of the longest songs* from each album, which, all things considered, may well be actual Peak Prog.*apart from one, which isn't on Spotify.