Specifically, the program is Barber's Second Essay for Orchestra; "L'altra notte in fondo al mare" from Mephistophele by Boito; the Intermezzo from Puccini's Manon Lescaut, Act III; the "Willow Song and Ave Maria" from Otello by Verdi; and Strauss's Ein Heldenleben. I forget where the intermission comes. The link to the performance detail page in my post at the time it was given is still active and gives you further links to the program notes.
This concert will be broadcast and streamed on January 2, and again on January 10, at 8:00 p.m., Boston Time.
You may also be interested in another "encore" from Tanglewood: the Tanglewood Music Center Orchestra with chorus and soloists performing Mahler's Symphony № 8 on August 8, 2015. WCRB's BSO page describes it as follows:
In an encore broadcast from the 2015 Tanglewood season, Andris Nelsons conducts the Tanglewood Music Center Orchestra and TMC Alumni, the Tanglewood Festival Chorus, the Boston University Tanglewood Institute Chorus, and the American Boychoir in Gustav Mahler's Symphony No. 8, the "Symphony of a Thousand," with a cast of soloists that includes soprano Erin Wall, tenor Klaus Forian Vogt, and baritone Matthias Goerne.(Emphasis added.)
My post has a link to the BSO's performance detail page, with a more complete list of soloists. This broadcast/stream will be on Sunday, January 3, at 7:00 p.m.
On Monday, January 10, we have the usual repeat of the concert broadcast and streamed a week ago, Mozart's final three symphonies, conducted by Christoph von Dohnányi.
Note that the WCRB BSO page has links to their podcast, "The Answered Question" for background interviews about both the Mahler and Mozart concerts.