In 1989, oboist Paul Dombrecht assembled a group of Belgian musician friends for a jam session. They had such a great time that their spontaneous meet-up evolved into an ensemble that specializes in lesser-known 17th—and 18th-century music. The group is Il Fondamento, and you can hear them play one of their discoveries on Sunday Baroque, starting at 7 a.m. on 91.1 and 107.5, and at 10 a.m. on 89.9.