Change Pitch of Song v2.0 will open the currently playing iTunes track in QuickTime Player 7 which will then continue to play it using user-entered pitch control settings.
This version now works in Snow Leopard but QuickTime Player 7 must be installed--even if QuickTime Player X is also installed. QTPX does not (yet) have the AppleScript support to use this script. QTP7 can be installed from the "Optional Installs" folder on your Snow Leopard installation disc. It will be installed in your /Applications/Utilities/ folder.