One of my favorite Mathis recordings, along with "Maria" (for which Sondheim was the lyricist, of course). As far as Sondheim scores, I especially like "Company".
Technically Anthology 2. Anthology 1 has later BN and Capitol tracks. The Capricorn albums are very nice indeed, an extension of the Hancock albums with the Mwandishi group.
I wonder what Impulse's trajectory would have been if Trane had lived and carried on. I would think they would have made it past 1978, which is when the lights went out at the label.