How do you get 12000 songs?
All of the songs on my iPod are first-rate. It's a lean, mean, "crap"-free machine! I imagine that those who have enormous iTunes libraries have two things in common: 1. a passionate love of music, and 2. eclectic tastes. To give you an idea how it comes together in one case, here's some of the genres, size of the genre, and sample artists from my iTunes library:
'50s Rock -- 1.47 GB (Elvis, Eddie Cochran, Gene Vincent, Buddy Holly)
'60s Rock -- 2.33 GB (Beatles, Stones, Who, Yardbirds)
'80s Rock -- 1 GB (Smiths, Cure, R.E.M)
Indie --- 1 GB (Pixies, Pavement, Liz Phair)
Metal -- 0.5 GB (Slayer, Metallica)
Punk -- 0.5 G (Sex Pistols, Clash, The Misfits)
Reggae -- 1 GB (Bob Marley, Burning Spear, Black Uhuru)
Dub -- 2 GB (King Tubby, Augustus Pablo, Lee "Scratch" Perry)
Hip-Hop/Rap -- 1 GB (Jay Z, Three 6 Mafia, The Pharcyde)
Blues -- 2 GB (Muddy Waters, Howlin' Wolf, Elmore James)
Funk -- 1 GB (James Brown, Parliament)
Soul -- 3 GB (Motown, Stax, Philly Soul)
French -- 2 GB (Serge Gainsbourg, France Gall, Francoise Hardy)
And on and on. Plus, about 2/3s of my collection is "classical", so there you're talking about loads of the greatest music in some of the great recordings of the century.
So, it can be done, and it offers all kinds of opportunities for playlists that bring together your music in a way that just isn't possible with CDs.
There you have it -- a recipe for an "All Killer/No Filler" massive iTunes music library.