Also, Kander and Ebb were perhaps the last songwriting team to become a "brand name" -- well-known enough, and so closely associated with each other, that you could just identify them by their last names: Rodgers and Hart, Rodgers and Hammerstein, Bock and Harnick, Lerner and Loewe,... and Kander and Ebb.
You can hear Ebb as a performer on a 1999 studio recording of Cabaret, where he plays Herr Schultz (I haven't heard the recording, though), as well as the Broadway Cast Recording, which includes, as an appendix, Kander and Ebb's demo recordings of several songs that got cut from the show (including one, "I Don't Care Much," that was reinstated in some later productions).
I'll quote an Ebb lyric from 70, Girls, 70 to close this:
Life keeps happening ev'ry day,
When possibilities come your way,
You can't start wondering what to say
You never win if you never play --
There's mink and marigold right outside
And long white Cadillacs you can ride
But nothing's gained when there's nothing tried --
Don't say "Why,"
Say "Why not?"
What lies beyond what is,
Yes, I can, yes, I will,
Yes, I'll take a sip, yes, I'll touch.
Yes, of course, yes, how nice,
Yes, I'd happily, thank you very much,