“Eres Tú” (“It’s You” in English), written by famed songwriter Juan Carlos Calderón, first became big when the Spanish male/female collective Mocedades performed on the 1973 Eurovision Song Contest in Luxembourg, a sort of American Idol showcasing the best of European music. The song came in 2nd behind Luxembourg’s own Anne-Marie David, but “Eres Tú” managed to find a bigger audience outside Europe, and it has the proud distinction of being one of the few Spanish language songs to break into the US charts (#9 on the Billboard Hot 100). It’s easy to hear how that could have happened; even in a different language, the song’s anthemic horns and uplifting harmonies makes it sound like a pop hit in line with the rest of ’70s Adult Contemporary ripping off ABBA. There’s also a flute, so that’s automatic street cred with the Jethro Tull crowd.
P.S.: Mocedades released an English version as a B-side called “Touch the Wind,” though that version has a different set of lyrics written by Mike Hawker rather than rewriting the original Spanish.