Bruno Mars and Anderson .Paak, who announced last week that they’ve come together as a project called Silk Sonic, have released the first song from their forthcoming album, and it’s a glorious blast of vintage R&B called “Leave the Door Open” that could be a Best R&B Song Grammy winner from 1974.

Even though the classic R&B sound the pair evokes is a decade older than they are, both the song and the arrangement are pitch-perfect, with swooning strings, honeyed backing vocals and even a glockenspiel — think Delfonics, the Chi-Lites and basically everything on the Philadelphia International label.

The duo announced the Silk Sonic project last week. “We made an album!!” enthused .Paak on Instagram. “Y’all get the first song next Friday 3/5!! Rocket emojis and all that!!!”

Mars confirmed the news and added that the moniker in the accompanying art is, in fact, a band name, though they’re not shy about also billing themselves separately. “We locked in and made an album,” wrote Mars. “The band’s called Silk Sonic. First song drops next Friday.”

Although not mentioned in the messages, the artwork makes an additional promise of Parliament-Funkadelic icon and legendary funk bassist Bootsy Collins as a “special guest host.”

The two have hooked up before, not on record but as tourmates when Paak opened for Mars on part of the “24K Magic” tour. The pair also put in separate appearances on the Chic album “It’s About Time” three years ago.

Mars’ last album, 2016’s “24K Magic,” resulted in the star winning the triple crown at the 2018 Grammys, where besides album of the year he picked up record of the year for the title track and song of the year for “That’s What I Like.”

Paak released his last album more recently — “Ventura” came out in April 2019 — but he’s been rife with one-offs since then, too. He put out four non-album singles just in 2020 (including a “Trollz” soundtrack collaboration with Justin Timberlake) appeared on a fifth (being a featured artist on Busta Rhymes’ “Yuuuu”).