The choristers of St. Paul’s Choir School in Harvard Square. (Photo: St. Paul’s Choir School)

The Boston Philharmonic closes out its 43rd season Friday, performing Mahler’s Symphony No. 3 at Symphony Hall in Boston with some strong contributions from Harvard Square: conductor and longtime Square resident Benjamin Zander, who founded the Philharmonic in 1978; and the choristers of St. Paul’s Choir School of the St. Paul Parish, at Bow and Arrow streets. The boys will provide the treble voices during the chorus behind the evening’s featured performer, Canadian mezzo-soprano Susan Platts. It’s the first collaboration between the St. Paul’s Choir and the orchestra. Boston’s Chorus Pro Musica will also sing.

Conductor Benjamin Zander. (Photo: Koren Reyes)

Zander, who’s lived on Brattle Street for more than 40 years (and whose sister is married to former Harvard president Neil Rudenstine), also runs the Boston Philharmonic Youth Orchestra, which he founded in 2012 to share his love of music with new generations. The BPYO performs May 6 at Symphony Hall, with 100 percent of the proceeds benefiting children with disabilities in Ukraine.