These collections are short (Ska is under 32 minutes) but satisfying. The ska collection balances familiar hits like Desmond Dekker's "007 (Shanty Town)," the Skatalites' "Guns Of Navarone" and the Ethiopians' "Train To Skaville" with lesser-known songs like the Dreamletts' perky "Really Now" and Toots and The Maytals' "Broadway Jungle," on which you can hear vinyl surface noise (you know it's a rare track when Trojan can't find the master tape in its bottomless vaults!). The 41-minute Dub album covers most of the major names in this instrumental genre. Its inventor, King Tubby, is represented by the Bunny Lee-produced "Blood Dunza Version" and Augustus Pablo's classic "King Tubby Meets Rockers Uptown." Lee "Scratch" Perry and the Upsetters feature echoes of Horace Andy on their dub version of William DeVaughn's "Be Thankful For What You Got." The veteran duo Sly and Robbie teams up with Mad Professor on the brand-new, extra-spacey "Stepping Out." There are also quality cuts by Gregory Isaacs, Black Uhuru, Prince Jammy, Culture, Scientist, Tappa Zukie and Linval Thompson. It's an excellent, wide-ranging introduction to this highly influential music.