All but one of the 18 songs on the new Pink Floyd album, The Endless River, are instrumentals. We asked David Gilmour how one goes about naming an instrumental track and he tells us it was his wife, writer Polly Samson, who came up with them.

Glimour explained, “One way or another they have a connection to the piece of music that they are describing.” For example, “Autumn ’68,” which features Rick Wright playing the Royal Albert Hall pipe organ, refers to when that took place, the autumn of 1968. And “Skins” is Nick Mason pounding the drums. Polly is also responsible for the lyrics to the only song with vocals on the album, “Louder Than Words.”