Alt-pop stars, assemble. Dan Smith invites some friends to give his filmic mixtape series a twist on this small-but-perfectly-formed collection of synth-driven collaborative jewels. The mash-ups and idiosyncratic covers that made Bastille’s name may be gone but the spirit of hooky bombast lives on (most potently on the spectral, shuffling “Axe To Grind”) and the features—including HAIM, rapper Lizzo, and the gravelly Rag N Bone Man—are uniformly excellent.