“There’s a very distinctive feel to the Blackwater Estuary, it’s almost Dickensian,” explains Paul Hammond, one half of Ultramarine. “It’s a very quiet, rural area with these mud flats everywhere – I think the river ended up seeping into our music.”

Paul and his musical partner Ian Cooper went to school in Maldon, Essex, at the head of the Blackwater Estuary, the stretch of water that inspired their shimmering, mysterious and gently meandering upcoming album Send and Return.

They began making music together in the 80s, releasing Ultramarine’s debut album Folk on Belgian label Les Disques du Crépuscule in 1990. Over the next decade or so, they recorded two John Peel sessions, collaborated with Robert Wyatt, toured the States with Orbital, then Europe with Björk. After a hiatus, they began recording again in Ian’s home studio, overlooking the Blackwater.

“We referenced the river in song titles, and Ian made field recordings of local birds, or his dog jumping into the water,” remembers Paul. In 2016, a film they made from Ian’s photos of the Essex estuary was screened at the Caught By The River Thames festival at Fulham Palace, London.

“It has grown into an ongoing side project which we named Blackwaterside after the traditional folk song performed by both Bert Jansch and Anne Briggs.” Ultramarine created two new pieces of music inspired by the estuary, released with an accompanying book, published by Random Spectacular, an imprint run by Blackford Hill’s Simon Lewin.

Following a performance on an island in the estuary and a live show in Colchester the day before the first COVID lockdown began, Send and Return is a brand-new installment to the project.

For the 6-track album, Paul and Ian hired a Thames sailing barge moored on the estuary for one day and recorded below deck in the ship’s downstairs wooden saloon; the idea originally inspired by seeing Robin Williamson of The Incredible String Band perform on a similar barge.

“It was a lovely space – where they used to store grain. If you listen closely you can pick up the wooden acoustic from the room. These ocean-going vessels would transport goods between London and Essex, which is where the title Send and Return comes from. It’s also a reference to mixing desk terminology, where you ‘send’ and ‘return’ sounds and add effects. We wanted to avoid a watery title for the album; this seemed nice and functional.”

The duo were joined by jazz musician Greg Heath and accomplished percussionist Ric Elsworth for the day, who added stunning saxophones, alto flute, percussion and vibraphone to the mix. It’s a contemplative, ambient record with gentle jazz inflections and softly pulsing electronica. Paul is pleased with the range of styles on the deliberately pared-back album, but also wary of over-conceptualising the work.

“We named the tracks after Thames sailing barges; Mirosa, Xylonite, Decima, Hydrogen, Reminder and Dawn. We’ve always liked the 6-track album format; the brevity and the way that it forces you to organise the record into two short suites of music. We thought this format would be a good way of setting some limits on the project and restricting any temptation to over-indulge.”

First track, Mirosa has an almost unsettling tone, casually brimming with a low-key dread in its machine-made beats, while the last track, Dawn is a peaceful, mellifluous closer, where warbling woodwind brings a bright, calm optimism. Elsewhere, celestial xylophone swirls around reedy sax lines then echoey guitar melodies drift and swell around bubbling vibraphone; the effect is transporting, meditative; invigorating then soporific in turn.