It has to be tough being Nick Cave -- taking off your coal-black trench coat, lecturing your lady about the darkness in your soul, calling down a curse from the Lord on the upstairs neighbors, and shooting out the lights. But the black-hole gravity Cave cultivates gives the Australian crooner asolemn authority that recalls his idol Johnny Cash (memorialized here on “Let the Bells Ring”).

Having good taste is easy; translating it into great art is another thing altogether. DJ/rupture and Diplo have both made their names as curators of different strains of the beat diaspora. Rupture links Middle Eastern dub to Jamaican dancehall; Diplo, of the raucous DJ duo Hollertronix, digs Baltimore club music and Brazilian baile funk. And when it comes to hip-hop, they both like it grimy.

This double CD’s first volume is easy enough to understand. It’s a collection of demos by Charles Thompson, who later became Black Francis and later became Frank Black. It was recorded in 1987, the day before his band the Pixies went into the studio to make their first record, Come on Pilgrim.