(Businessweek) — Compared with buying e-books, building a digital music collection is a hassle. E-books zip directly to reading devices like the Kindle and Nook and are backed up “in the cloud”—on the servers of Amazon.com (AMZN) and Barnes & Noble (BKS). A digital song, on the other hand, is typically downloaded to a PC and must then be manually transferred to an iPod or mobile phone. If you lose your Kindle, you can always download an e-book again; if the PC crashes or the iPod falls into the bathtub, the song goes down with it. Moving music to the cloud has been an elusive goal for big tech companies and their music industry counterparts, until now. In the past two months, Amazon and Google (GOOG) have unveiled cloud music services, albeit to mixed reviews and indifference from consumers. These new services let users upload their music collections into so-called digital lockers on the Internet and stream the songs they own to a variety of devices. Both are limited, because neither Google nor Amazon could reach an accommodation with music labels. Label executives say they are negotiating aggressively to make sure they profit from the shift to the cloud. It may be the last opportunity to stem rampant piracy and years of plummeting sales.