Anderson .Paak was at Boston Calling Music Festival on Sunday for the latest stop on his ongoing Best Teef In the Game Tour. .Paak’s festival performances have become a headline-worthy spectacle in their own right, as earlier this year the Ventura singer surprised attendees at Coachella by welcoming late-90s pop artist Brandy to join him on stage. For his set at Boston Calling on Sunday, .Paak again welcomed a surprise guest. This time, it was controversial hip-hop/country crossover sensation Lil Nas X. Together, the two treated the audience to a duet performance of the rapper’s chart-breaking 2018 hit, “Old Town Road”.

Related: Anderson .Paak Appears On ‘CBS This Morning’, Performs Music From ‘ Ventura’, ‘Oxnard’

The surprise sit-in started with .Paak’s keyboardist hammering away on the keys for a few different songs before transitioning into “Old Town Road”. Lil Nas X found his way to the stage in his trademark cowboy hat and a flame-embroidered black and white leather suit–a bold move during a hot holiday weekend. Lil Nas X’s presence at the festival had been hinted at by organizers, as the artist was billed as a “Special Guest” going into the weekend event.

Watch the opening portion of the sit-in performance from Sunday below.

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@lilnasx stay focused bro! #bostoncalling2018

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.Paak continues his spring tour with his next scheduled performance at the MECU Pavilion in Baltimore, MD on Tuesday. Head to his website for tickets and tour info.

[H/T Billboard]