Tjårnblom celebrates its third CD, “Woods,” at the American Swedish Institute in Minneapolis, this Friday at 7PM. But this new project marks big changes to the group. Joining Tjårnblom is a new member, cellist Erin Walsh, joining Val Eng on the harmonium, mandolinist Joe Alfano and nyckelharpa player Cheryl Pashke. When Joe and Cheryl talked to Phil Nusbaum about Tjårnblom, Cheryl first addressed the long-standing mission of the group.