As the Thetford Chamber Singers enter their 40th year of sharing sacred and secular music with Upper Valley audiences, it seems appropriate that 40 vocalists should breathe life into the concert “Remember.” This spirited program includes selections spanning the 16th through the 21st centuries, spotlighting composers from Johannes Brahms to 37-year-old American songsmith Abbie Betinis. Vermont composer Roger Grow is among choral music heavy hitters as his TCS-commissioned work, “Ghost of the Past,” debuts in concerts in Strafford, Woodstock and Thetford. Kevin Quigley directs the powerhouse singers with piano accompaniment by Matthew Wiencke.