If you really want to make music professionally, then I recommend hardware. Not software.
If you have the money, you can go out and get you a Korg Triton or m3. Top Notch. Also, you may wanna pick up a MPC2000. Of course both of those
things will run you a good $5000 brand new. You could look into a pawn shop though.
Korg m3
image source: http://www.korg.com/page_img/m3_center.jpg
Korg Triton
image source: http://www.korg.com/gear/images/products/enlarge/lrg_TRITONPROX.jpg
Akai MPC2000
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www.sequencer.de...[/im]
Another alternative besides hardware is some really good software. If you're looking for software you can get started pretty cheaply with a decent
MIDI Keyboard ($150) and Propellerhead's Reason 4 ($600). That will get you started makin some pretty sweet music. I used Reason to make the song
below in my signature. Just load up some sounds and play em on your keyboard while you're recording.
Reason 4
image source: https://www.propellerheads.se/shop/img/category/topstory-rsn-405px.jpg
Also, if you have a Mac, then I recommend Apple GarageBand. Its a pretty neat all in one package for recording and making music.
Apple GarageBand
image source: http://images.apple.com/ilife/garageband/images/hero20070807.png
These are of course professional options that I would recommend to those who are serious about it.
If you're just looking to dabble around a bit, I recommend Fruity Loops, as you can find a version of it just about anywhere and its got a relatively
low learning curve.
Fruity Loops Studio
image source: http://www.fruityloops.com/documents/GiantScreenshot8Mirrored.jpg
And for professional recording, one cannot beat ProTools. I personally use it with the digi003 mixer and it is the SH**! Assuming you have about
$3000 to kick around...if not I recommend CoolEdit 2.0 for recording! It is very sweet also. I think its now called Adobe Audition though...I dunno,
its been a while since I used it.
you can find the respective softwares here:
Propellerhead's Reason 4.0
Fruity Loops
Apple iLife GarageBand
DigiDesign ProTools 7 (Recording)
Good Luck to you man!