Putting A Studio Together

So I've got a synthesizer. I'm beginning to learn how to use it. Now I need to find a way to capture what I'm doing. I need a few things:

1. A way to record MIDI. That is, to capture the notes I'm playing on the keyboard to clean and fix them before recording the audio.
   
2. A way to record audio.
   
3. A way to put multiple tracks together to make a song.

So I found the M-Audio Fast Track USB audio interface. It's got a direct line for things like keyboard or guitar, as well as a microphone port for voice and acoustic instruments. It works fairly well, other than I currently get a high-pitched hum when capturing audio that I haven't been able to filter out yet.

Then I got some software, Cakewalk Sonar, home studio for digital recording, sequencing, MIDI, and all sorts of things, including the ability to use Software Synthesizers (virtual synthesizers that only exist through software emulation) and other effects including virtual drums. When I was 17 I got one of the first versions of Cakewalk on our first PC. The product is nearly unrecognizable now from that early version, but I do have some history with it.

I'm still trying to figure out just the simplest options in Sonar, but I've figure out enough to start putting some music together.