> it's not worth my 30 seconds to unlock my phone
It takes me ~4 "seconds" (saying "one-one thousand" aloud) to do it when typing in a password (sorry, don't have a stopwatch handy). Just did it 10 times just to test. It'd be even faster with pin/fingerprint/face unlocking, or with no locking at all.
I also used Shazam and Google's "what song is this" feature for somewhere less than 5 minutes on the initial few seconds of 10 songs and my battery indicator didn't move a single percentage during my testing. Shazam scored 10/10, Google missed one (a song from an esoteric Chicago band called Terminal Bliss - all of the songs I chose were intentionally fairly obtuse to try to find missing info in the databases).
But I can say with fair assurances Google's not shipping their entire database on phones, just whatever's most popular up to some (probably size driven) limit; any given CD releases with about ten songs, any given year sees tens of thousands of CD releases (about 75,000 albums in 2010 alone). Worse, the entire feature's use case is better suited towards less popular music since you're less likely to know the song's name if it's new or esoteric - so you can almost immediately guess that those 70k songs in that database is just ~30 years of various genre chart topping hits.
All you've done is cement my convictions that this is absolutely a solution in search of a problem.