Note: I was not able to get access to a page with just this abstract on it; therefore this reference is about a third of the way down the page linked to below.
From a study by Mammarella N, Fairfield B, and Cornoldi C:
METHODS: With a repeated-measures design, older adults were presented with the forward version of the digit span and phonemic fluency in classical music, white-noise and no-music conditions. RESULTS: Classical music significantly increased working memory performance compared with the no-music condition. In addition, this effect did not occur with white noise.
For years, children have claimed that they get better results when they study listening to music, and they were right–however, now we learn that studying to classical music works with older adults, too. So when your boss comes by and tells you to take off those headphones, smile and point him at this study, and tell him science proves you need that classical music to increase your productivity.