The Ocean close Solaris with Tangerine Dream's Thorsten Quaeschning on a new track

The Ocean have put out Milk of My Dreams, and it is not a conventional single so much as the last piece of a jigsaw. The track finishes a 20-minute closing chapter on Solaris, the German collective's twelfth album, which arrives on 25 September. It follows Ultima Esperanza in sequence on a record that runs to 70 minutes.

The guest is the detail worth correcting, because it is easy to get wrong. The collaborator is Thorsten Quaeschning, the man who has led Tangerine Dream since Edgar Froese's death, rather than the group as a unit. His synths and sound design shape the track, which sits in a darkly electronic, trance-adjacent space a long way from where a post-metal band usually ends an album.

The band, all of them long-standing Tangerine Dream listeners, described the sessions as an honour and were specific about why. They praised his knowledge of electronic music, synthesizers and sound design, and his ability to take a sound somebody can only describe in words and turn it almost instantly into something audible. "His studio feels like a synthesizer museum," they said, everything connected, switched on and ready to play.

Quaeschning found the collaboration harder than his usual work, and for a technical reason that explains a lot about how The Ocean write. "I had to adjust some of my usual working methods," he said, because the band's music moves through so many shifting time signatures that most hardware step sequencers stopped working the conventional way. Rather than programme individual two, three or eight bar sections, he played many of the sequences by hand, which he reckons gave them a more organic feel through dynamics, touch and small timing differences.

The track's origins set it apart on the record as well. Most of Solaris was a pandemic project, written years before release, while Milk of My Dreams is recent work written last year by Enrico Tiberi, the collective's new vocalist. That makes the album's final movement the newest thing on it, which is an unusual way round for a record with this long a gestation.

Metal Injection, carrying the premiere, reached for Depeche Mode and Enya to describe where the track lands, which is not a comparison many bands on the metal rail get. Bringing in an outside specialist for a single track has been a live tactic in the genre this year, with Wayfarer enlisting David Eugene Edwards for Perdition's Crossing and Sleep returning with The Morrisist ahead of their own album. Release dates sit on the release calendar.