Basically what Razzorman wants to say, but said more nice:
If you want to create your own music for your KS levels, you'll have to understand that making music isn't as easy as creating a level for KS. There's a much steeper learning curve for learning the music program even for the simplest and most easy to learn programs. Secondary, the learning curve for creating good music takes years.
It is an awesome experience to undergo, but it will probably be that you've lost interest in your KS level long before you have any decent music abilities.
I'm very good in making music, but I'm doing that for more than 15 years now. When I made music for 2 years, I really sucked. I found myself good at that time, but now that I listen back to it, it was horrible. You'll be able to make some nice songs with a year experience, no doubt, but calculate a 2 year time period of making music often to get to a level where quality becomes a factor and it will be suitable for anything you want to be proud of.
Music creation comes in several stages.
Time is a rough estimation. Can vary for anyone, its just so you see how much it takes to get good at this.
1. Learning the program from the inside out (1 month)
2. Learning to combine sounds to form music (1 year)
3. Learning to not just add stuff to what you already have, but actually create variation (another year)
4. Put emotions in it (2 to 3 years)
5. Mixing your songs to enhance quality (4 years, though you'll get decent results after about 6 months, the rest is finetuning)
6. Master your songs to get a better overall quality (same as above, because its the same learning curve)
7. Usage of advanced features like plugins (depends on the extensiveness of the plugins)
8. Learning about hardware related instruments to understand their software equals (4 years if not more)
9. Learning technical aspects of music, such as chords, rythms, chord progressions, etc.
Not necessarily in that order.
Although you only need the first 3 to make descent music, and there's always more to learn, this is a rough sketch of what will await you when pursuing the art of music.
Now, this certainly is not meant to be discouraging. In fact, you really should try it. It is very fun to do, it just takes time.