Another music notation software package that I have experimented with this week is Notion.  It is available for purchased download for PC or Mac for about $50. Or as an app on the iPad for about $14. I think it is that the closest thing that I have found so for to Finale for the iPad.  Initial price is cheap but you must make in app purchases to get all of the sounds.
 Check it out.
http://www.notionmusic.com