Boston’s Symphony Hall is widely regarded to be one of the finest concert halls in the world, both acoustically and architecturally. And this past summer, one of the most distinctive features of the hall, the 1900 Hutchings organ, underwent a historic tuneup. “In February, [organ builder] Foley-Baker removed the innards of the organ, took apart the electro-pneumatic engine that makes the whole thing work and has been analyzing and rebuilding the elegant old machine. It’s the first major reconditioning since ’49, and includes installation of many of the pipes [that a previous restorer] planned to use in the first place.”