From Microsoft Watch: Microsoft and Apple are continuing to trade barbs over operating-system leadership (in spite of Apple's decision to allow Windows to be dual-booted on Intel-based Macs). The latest: Microsoft is working on a competitor to Apple's GarageBand music-making program, according to our sources. Microsoft isn't talking, but we hear the forthcoming Microsoft music-creation applet, code-named "Monaco," is being optimized for Windows Vista.