I've been digging into Blue Bossa and it's generated a question: how do harmony players typically voice that first chord in your experience? According the New Real Book, that chord is a C-6, but the pianist could pick the Natural 6th or the flatted 6th. Listening the 1971 Joe Henderson recording Live in Japan, it sounds to me as though Hideo Ickhikawa is playing a C-7 and not a 6th at all. I suspect that many of the pianists I've played with do the same, is that your experience? I think my preference is for the Natural 6th because it creates movement between the C- and F- chords and is a more interested note than the minor 7th. Do you have a preference? If so, do tell!