Most of the recordings on this collection of songs by tango's modernist master, including a heart-warming rendition of the great Vuelvo al Sur, date from the era of Piazolla's New Tango Quintet, formed in 1978. A soundtrack to Buenos Aires, this compilation with expert liner notes, chosen by music critic Robert Christgau as one of the best albums of 2005, belongs in your collection.  (ARG60, $14.95)