The MET Orchestra Chamber Ensemble takes extraordinary musicians from the orchestra of the Metropolitan Opera and allows them to ply their craft in more intimate and stylistically flexible configurations. In the fourth of six concerts this season, the ensemble performs an assortment of 20th-century works, including a playful Martinů sextet, a delightful piece by Ravel, Takemitsu’s spacious and spellbinding Rain Spell, and one of Böhme’s definitive compositions for brass.