I've copied this from the notes under that YouTube clip. So, on half the songs, what you hear is what was recorded live with the strings. Remarkable.
"As noted in the booklet for the 1997 CD reissue, Sauter's orchestration did not include melodies for Getz. Rather, Sauter left spaces in the arrangements in which Getz would improvise. Documentation for the recording dates is incomplete, but the CD booklet reports that those involved in the original sessions recall that Getz recorded live with the strings on about half the songs, while he overdubbed sax solos on the others.
The theme of the opening track, "I'm Late, I'm Late", is nearly identical to the opening minutes of the second movement of Béla Bartók's Music for Strings, Percussion and Celesta. Bartók had been an early supporter of Sauter, who intended the track as an homage. "I'm Late, I'm Late" also features drummer Roy Haynes, the album's only soloist beside Getz."