Thank you, Klingsor. Before I set down my reaction, I should note that I'm not a great jazz fan. I enjoy some John Coltrane, Albert Ayler, and Mingus, as well as jazz standards such as Ella, but I don't listen to a lot of jazz. And I listen to almost no klezmer music.
That said, the excerpt of Caine's version of the M5 funeral march movement didn't work for me. It sounded not like music for the funeral of some great personage (Mahler himself, for example) or, as it sometimes does , like a funeral for us all, but like the funeral music for somebody's uncle, who perhaps ran the corner deli.
Caine's version lacked grandeur and emotional impact. I didn't care about the person who had died, and his or her death didn't seem universal, but a particular and parochial experience.
When, shortly after the 4-minute mark, Caine and his group seemed to switch from klezmer to jazz, that didn't work for me either. It lacked the craziness of the wild sort of jazz that sometimes appeals to me.
Mahler was, of course, one of the greatest orchestrators of symphonic music. That doesn't mean his choice of instruments, etc. is sacred and untouchable. But it does set a very high standard for those who would re-interpret his basic materials. In this instance, I don't find that Caine was successful.