Are you referring to the "Mozart Effect" studies? That's what I found in the book (or at least the parts of the preview that were accessible), but Mozart is actually classical, not baroque. The effect seems to be small and specific to one particular type of task, according to this Nature meta-analysis:

Rauscher et al. 1 reported that listening to ten minutes of Mozart's music increased the abstract reasoning ability of college students, as measured by IQ scores, by 8 or 9 points compared with listening to relaxation instructions or silence, respectively1. This startling finding became known as the 'Mozart effect', and has since been explored by several research groups. Here I use a meta-analysis to demonstrate that any cognitive enhancement is small and does not reflect any change in IQ or reasoning ability in general, but instead derives entirely from performance on one specific type of cognitive task and has a simple neuropsychological explanation.

As a side note, if you're going to cite studies it would be great to continue Romeo's trend of actually linking to the relevant studies, since there's not enough info in your comment to find the ones you're referring to and I don't own Wiseman. I don't really trust Wiseman (or pop-sci books in general) to interpret findings with anything remotely resembling rigor.