Instruct: Classify Amazon reviews into positive or negative sentiment
Query: A subtle masterpiece

Blue Lines invented trip-hop and electronica, which in and of itself would be enough to make the album a classic. But just as impressive is how Massive Attack uses their genre-inventing sound to frame and mix a variety of established musical styles, including hip-hop, reggae and soul. They mix these elements seamlessly and the musical alchemy reaps intoxicating rewards. Much of Blue Lines' success is due to the sublime performances from the album's three vocalists: rapper Tricky, reggae artist Horace Andy and R&B crooner Shara Nelson. Everything comes together so smoothly on Blue Lines that the casual listener might not even notice how groundbreaking it is.