Nothing against Gustav Mahler's nine symphonies, but most of them are massive, angst-ridden affairs. They ponder great questions on the meaning of life and death in ways that can be downright, well, ponderous. Which makes the smaller, lighter, tender Fourth Symphony all the more charming. We'll hear three movements from Mahler's Fourth, from a concert at Amsterdam's Concertgebouw. Plus, Johannes Brahms giving credit where credit wasn't due: his "Variations on a Theme by Haydn," which wasn't by Haydn at all.