Here’s proof that big things come in small packages: At a piddling 1.8 inches, Sony’s NW-HD1 is the industry’s most minuscule 20GB digital music player. Units store 13,000 songs — ­ offers more than 650,000 compatible tracks — in the ATRAC3 audio format, into which WAVs and MP3s can be converted. A rechargeable lithium ion battery packs 30 hours of playback, almost three times more than Apple’s iPod. Now that’s worth partying about. $400.