I understand Anvil to be a pretty flexible application for its "pricetag." There are a also many low-cost alternatives that offer a lot of extended features. It's kind of cliche, but FL Studio is a good place to start if you're new. Writing music in sequences is easier for most people (assuming they're writing in the common time.) It also offers full VST / DXI and midi control support, and lets you export your music as .wav or .mp3 (which you can convert to .ogg.)
What kind of musical background do you have? Do you have any experience with sheet-writing? If you have any experience there, it should transfer to midi writing pretty seamlessly. If not, don't expect it to be an overnight project. I started three years ago and I'm still learning every time I write something.
You will need to make yourself familiar with midi commands in order to get the kind of control you want over your songs. I'm honestly not sure if Anvil has this capability or not, as I don't use it. All of the default songs packaged with the RTP use midi commands to change things like pitch, mod and velocity. Looping your midis from a specific point also requires using midi commands.