Yeah, that Judas remix.. how bout that. :P A solid 4 months have now passed, anddddddddd I got no more done on it, but I fully intend to finish it sometime! I'm actually doing an EP now so that's an okayish excuse, innit? :P Also college exams. :(
Well that should certainly help you then; the thing to input notes is known as a 'Piano Roll', so you just need to know what notes are what to actually be able to make melodies and stuff. I started with FL Studio and still use it today. A lot of people use Ableton (famous producers/DJs such as Laidback Luke and Skrillex for starters), but I haven't quite gotten the hang of it. I'd recommend starting with FL, but it really is entirely a personal thing. :)
I've been playing musical instruments since the fourth grade, so I do have knowledge in music, though I don't have any knowledge with piano. Because of being involved with it for so long, I somehow feel obligated to continue being involved with it in some way. I've made some compositions in the past, and thought of going into production for a while, but never really knew where to start. I have almost all of Lady Gaga's acapellas at very high quality, so I can always use those once I get into remixing!
I've played piano since I was about 5. That's by no means a necessity, but a knowledge of piano notes pretty much is. You then need software to MAKE the music (known as a DAW). In general all music making DAWs are faaaaaaaairly expensive, so you either make do with trial versions or.. other ways, wink wink.
Such software's are: FL Studio, Ableton, Logic, Reason, and Pro Tools. I started out with, and still use FL Studio. It recieves a bit of 'hate' because of its apparent user-friendliness, but I really think its a great program. There are literally thousands of tutorials on YouTube, too :)
At first I mainly did mashups, which often involved literally getting two MP3s of songs that matched and.. mashing them together. Then I began remixing; to do that, you need the acapella file of a song. A place I use for acapellas is 'acapellas4u.co.uk'. The only downside is, it's very, very hard to find acapellas at their highest quality, but most people manage :)
Is there anything I might've missed that you'd like to know more about? :)