The organ at St. Mary’s was built in 1986 by the firm of Karl Wilhelm, Inc., Mont St. Hilaire, Québec, Canada as their Opus 109 (Wilhelm’s first organ in Massachusetts). The organ consists of 20-stops and 23-ranks of pipes…a total of 1,184 pipes…played via mechanical key and stop-action from an attached keydesk of 2 manuals / 56-notes and a flat pedalboard of 30-notes.  The natural keys with their bone facings and the sharps of rosewood, together with the drawknobs of rosewood, provide a contrast to the stained and oiled oak of the case. The casework is made of white oak joined by rabbeting or tongue-and-groove methods. There are no nails or screws to join the case together, nor any metal framework or supports for the organ case. The carved pipeshades recall with their design the carvings of the earlier reredos behind the previous altar. Metal pipework is made of  varying percentages of tin and lead, while wooden pipework is made of white oak. On-site final tonal regulation was accomplished by Martin Pasi and Karl Wilhelm. The organ received its dedicatory recital by Wolfgang Rübsam on 25 February 1987. In 2002, the organ was rededicated to the glory of God and named in honor of the Rev. David E. Allen on the occasion of his retirement as Rector (1979-2002).