Yup.....

Not necessary for most styles of music you'd make on a computer. However I strongly recommend at least skimming through this:
https://www.dropbox.com/s/a0v7yxkshezyufr/rsg-0.8.1.pdfIt was a great help to me when I was trying to get to grips with chords, melodies, keys etc.
I started with MusicLine Editor on the Amiga, then moved on to Reason, Reaper and then Studio One. Sadly I don't find the time or inspiration to make anything these days, but it's very fun and rewarding when you have the motivation.
You'll have to find what works best for you You've got your old-style trackers like ProTracker, OctaMED etc. and there are also modern trackers that support VST plugins (virtual instruments and effects). Then there are loop-based editors like FL Studio, Ableton Live etc., and then there are linear editors like Cubase etc. There are also hardware sequences, groove boxes etc. (Electribe and so on). Trackers are probably the least intuitive to work with, but some enjoy working within set boundaries/limitations (it's easy to get overwhelmed with a modern PC DAW, tons of VST's etc.).