[Musicology - IU v. BU]

Not sure about BU's program, but IU is pretty top-notch for medieval music (and they just added Michael Long to the faculty: http://info.music.indiana.edu/news/page/normal/21614.html).

[Musicology topics]

Rowdy, I've been a career student, but this was really helpful for me in determining the value of graduate study in general: http://www.quora.com/Graduate-School/Is-going-for-a-Ph-D-worth-it-if-Im-extremely-passionate-about-a-field-but-dont-really-want-to-spend-my-20s-poor-toiling-away-in-a-lab-and-living-in-a-city-that-I-dont-particularly-want-to-live-in/answer/Mark-Eichenlaub

Keep in mind that your area of interest (the history of Jewish sacred music) is a specialty within a specialty within a specialty. So when choosing programs, don't settle! You want to work with people who are as passionate about your field as you are.