Millennium Park’s Jay Pritzker Pavilion began its “Downtown Sound” concert series this week — with shows on Monday and Thursday evenings. On Thursday, June 4, the Very Best gave an exuberant performance that got many audience members dancing. The group is a collaboration between Radioclit (a London-based DJ/production duo) and Esau Mwamwaya, a singer from Malawi. At times, the music sounded purely African; and at a few moments, the electronics gave it spooky textures. But more often, it came across like party tunes, replete with singalong refrains. The opening act, Chicago dance band Glass Lux, played synth pop songs that sounded straight out of the 1990s.