"Txai" is described as a term of respect for those who are allies of the forest – and such is the focus of this concept album, the end result of a fact-finding voyage through part of the northern Brazilian watershed. Utilizing forces ranging from a simple dialogue between Milton Nascimento's baritone and percussion to a large orchestra and chorus (often arranged by Wagner Tiso), Nascimento shares his thoughts about the rivers and nature, ultimately warning us not to let the forces of capitalism destroy the Amazon rain forest (reinforced by a spoken passage written and narrated by actor River Phoenix). The songs are separated by wild-sounding interludes of folk music from the peoples of the region, and there is a fascinating vocal/percussion arrangement of Heitor Villa-Lobos' "Nozani Na."

To lovers of Brazilian jazz, the pairing of these two legends of the genre amounts to something of a musical orgasm. The only serious misfire isn't really that bad, just a bit incongruous. Why would two consummate Brazilian ambassadors choose to do their one English lyric song – George Harrison's "Something" – as a reggae tune? The groove is silly, but actually some of the guitar work is fun. Just as when Ivan Lins sings in his native Portuguese rather than stilted English, this tandem is most at home conveying emotions that go beyond simple semantics, usually with Gil writing the music and Nascimento the lyrics. "Sebastian" is a moody bass-and-drum driven power ballad which functions as a showcase to their raspy vocals. The romantic, accordion-enhanced "Duas Sanfonas" would be more effective without the guest vocals by Sandy and Junior.