Sergio Mendes & Brasil '66 went to Japan to perform at Expo '70 and brought Bossa Rio along as the opening act. Both concerts received an LP in Japan, but the Bossa Rio album is a bit harder to find.
Here from that concert, and album, is the song "Canto de Ossanha" also known as "Chant of Ossanha" or by its more common English title of "Let Go".
The song had been performed by The Sandpipers, Astrud Gilberto, Tamba 4 and many others.
