When his record company issued a pricey box set of his music, Elvis Costello tookthe unusual step of telling fans to buy the Louis Armstrong "Ambassador of Jazz" setinstead. So we did. And he was right, it's first-class. If you're one of those who thinksmusic started with the Black Eyed Peas, try Satchmo's version of "The Faithful Hussar,"which he also played when he was at the Lucerna in March 1965. The biggestsurprise of the box set is actually the "Slivovice Interview" from May 1965, where hetalks about his trip to Prague and about having to "leave that slivovice alone ... becauseit'll knock you out." The next day, he said, "that hangover is something, boy."He also said they gave him a beautiful trumpet in Prague that he keeps as one ofhis choice possessions. The people behind the Iron Curtain seemed pretty happy, hesurmised: "They have everything they want, they just can't come over on this side."