What makes it so is that these performers — the singers, of course, but also the jazz combo — perform with a real awareness of what made this music tick for the churchgoers of the distant past, and what it needs to be made to tick today. There is a fine, elegant slitheriness in the parallel movements of archaic harmonies (“fauxbourdon,” you remember from Music 101) and an exaltation in the outbursts of “Alleluia” that keep things moving. No, this kind of crossover activity doesn’t answer the problem of how to bring medieval music to life in contemporary jazz clubs. All I can say is that this project is the work of honest, enthusiastic musicians bridging what used to be regarded as an unbridgeable chasm. The result is 62 minutes of music not at all disgraceful and — as a matter of fact — decidedly not bad.