Northborough – Several dozen people, young and young at heart attended a concert by the duo “Knock on Wood” May 16 as part of the Northborough Free Library’s Spring Music Series. The high-energy acoustic folk-rock duo, combining witty banter, original music and covers of classic rock bands such as the Beatles and the Kinks, offered something for everyone. Members include Howie Newman, Joe Kessler and Steve Latanision.