It's already a tweet but worthy of a blog post : a few minutes ago, edenx, my "proof of concept" OSX version of Rosegarden, has just made its first noise. Played its first 3 audible notes (for posterity, those are in chromatic progression starting at middle C).
Some quick facts : the UI is a bare bones "Tracker" : a track list and an event list, with a 'Play' button (will post screenshots and possibly a screencast later). It can save and load documents, and has undo/redo. In total, about 900 lines of code, out of which you can remove about 100 lines for a scrollview synchronizer which I've copied from an Apple dev document. It's hard to estimate how long I've spent time on this so far. Initial setup of the svn repository was done in mid-may last year. I resumed work on this in late february I think, with a first commit on march 1st. I estimate I've spent an average of 10 hours a week on this since then. That's including browsing the Apple dev docs to look for info on stuff not covered by Aaron Hillegass' excellent Cocoa Programming for Mac OS X posting on the cocoa-devel mailing list and bugging my friend Florent for help.
These facts are all very pointless by themselves, you need to compare them to how long it took Chris, Rich and me to get RG to make its first sound back then (although we also had a notation editor at this stage too - a pretty hefty piece of work).