Summer’s almost here, and the time is right for some sunny pop escapism. Newly blond-and-shorn Katy Perry tries to escape from escapism on her recent single “Chained to the Rhythm,” a dance track with a vague message of empowerment and anti-conformity that’s buried by lightweight production. Perry is more enticing on the bubbly new single “Bon Appétit,” in which she and rappers Migos make the most of a simple eating-cherry-pie metaphor and turn it into a moderately salacious, Madonna-style diversion. The rest of this year’s Wango Tango bill is a mixed bag that ranges from such young pop hopefuls as actor-singer Hailee Steinfeld and Santa Clarita songwriter Julia Michaels to less compelling mainstays such as Backstreet Boys and Maroon 5. Rapper Machine Gun Kelly duets with Camila Cabello and could reprise “At My Best,” his recent collaboration with Steinfeld.