Here's a good one! Ozzy Osbourne and Earth, Wind & Fire walk into a bar, and this mashup by DJ Cummerbund is the result!
This mashup is made up of the vocals from "Crazy Train" by Ozzy Osbourne and the instrumental track from "September" by Earth, Wind & Fire." It is a very well-constructed mashup, and it has a lot of positive things going for it. Generic contrast is set up well by positioning Ozzy Osborne, a heavy metal musician, against Earth, Wind & Fire, an R&B/disco group. The raw/slick contrast is important in constructing a mashup, as I have mentioned in my published work. The structure of both source songs is similar: they each contain eight-measure verses and eight-measure choruses, and while "Crazy Train," contains a pre-chorus that "September," does not include, it is also eight measures long, making it easily graftable into the finished track.
Harmonically, the fit is strikingly good. Neither songs are pitch shifted, either. "September" is slightly slowed down, so that the tempos match, but no adjusting for key needed to be done. "September" is in D major, and "Crazy Train" is originally in A major. Ozzy's vocals are not transposed, but simply heard as being recontextualized in the key of D with Earth, Wind & Fire's instrumentals. Harmonic recontextualization of vocals, especially when it involves a change of key, is one of my very favorite features of a mashup. However, the one complaint I have about this mashup has to do with one specific place where the recontextualization doesn't work very well. At the end of the chorus, Ozzy sings, "I'm going off the rails on a crazy train!" DJ Cummerbund cuts off his vocal line fairly early and doesn't let him hold onto the note he's singing, an F-sharp, for very long. However, the effect is still quite odd. The chord at this point is a G major triad with an add-2 (or a 9th). The F-sharp in the vocal line, then, gives the impression of a major seventh on the chord, which, in my opinion, changes the sonority too much. I can't fault DJ Cummerbund for putting this together, though. It is well-crafted, and the verse sections fit together so perfectly. It needed to be shared with the world!