If you need to focus in math, then Mozart should be your music of choice. A colleague of mine, Fran Rauscher, was the lead researcher in what was called "The Mozart Effect" about 10 years ago. The basic meat of the research shows that students who listen to Mozart experience a boost in their spatial-reasoning skills (math, sort of). Here are some highlights:
In 1993, a pilot study found that preschool children given music training displayed significant improvement in spatial reasoning ability. (Frances Rauscher, Gordon Shaw) An experiment with college students found that, after listening to a Mozart sonata, they experienced a significant although temporary gain in spatial reasoning skills (Frances Rauscher, Gordon Shaw and Katherine Ky, Nature, Vol. 365 [1993]: 611).
In 1994, a Stage II follow-up to the pilot study again found that music training improved spatial reasoning in preschool children. This gain did not occur in those without music training (Frances Rauscher, Gordon Shaw, Linda Levine and Katherine Ky, Paper presented at the American Psychological Association, Los Angeles [August 1994]).
In 1995, a follow up to the first Mozart study confirmed that listening to Mozart improved spatial reasoning, and that this effect can increase with repeated testing over days. However, the effect may not occur when music lacks sufficient complexity. (Frances Rauscher, Gordon Shaw and Katherine Ky, Neuroscience Letters, Vol. 185 [1995]: 44-47.)
Do a search on Frances Rauscher or "The Mozart Effect," for a ton of links.