I'd highly recommend the following:

Buy yourself a copy of the following software: Steinberg's Cubase (specifically this software instead of the more common FL studio, and Ableton - because it's made for arranging linear musical events and has excellent expression control which you will need when you are trying to emulate human player expression. A High quality symphonic sample based library (VSL, Berlin, SWAM, Audio Modelling - check out VI-Control forums + KVRAudio forums for indepth discussions on the merits of each. You will need to combine several to get breadth. Grab yourself a VST (software) Bass guitar (?? look this one up im blank off top of head), drum sample library (DrumKit from Hell 3), electric guitar sample library (Shreddage).

So thats all the software more or less. You will need a beastly computer to run these live with human latency figures (vicontrol forums talk extensively about computer and processor architectures which are best for composer workstations - intel i9's are pretty popular for pro stations).

For composing - the piano roll will be your friend. As you're a coder, copious amounts of clicking shouldnt deter you...playing things in with keyboards like a pianist is fine - but requires you develop the mechanical skills to do so.

There is a lot of literature + youtube videos about the theory. Your first goal should be reproducing a metal tune...using your software instruments. A second goal - some sort of simple symphony.

The comment about transcription is key - you will need to develop an ear for what the composers are doing. You will need to start embarrassingly simple - and build. Starting with romantic era composers as a target will end in tears.

Happy to chat (my email is in profile) if you have questions.

One of the most underrated reasons to go to that site is the solid and extremely supportive community. You can start with any piece of software. I highly recommend https://ableton.com because it is designed to support live performance and has a very strong following

Beyond that, music is the expression of yourself into the outside world through sound. This can mean ANYTHING. The most effective way I've found to start this and pretty much any other creative task is to follow what you find interesting. Self-motivation is the tough part here and you've already started pushing up against that. Great job!

8-bit music is a place to start and given your list of music you really REALLY should avoid making music software (I HATE the word "should" but in this case I have 4 decades of experience so I'm leaning in). You'll feel comfortable doing it and you'll make cool stuff, but in my experience it pulls you away from the emotional connection to the work. The genres you mention are very feeling oriented.

Get yourself a simple MIDI keyboard or pad machine for drums to start. Use your body. Associate yourself with the movements so you can FEEL it as you make the music.

It will take a LONG time to get to a degree of proficiency and every time you make some music in 10 seconds you'll wish it was better. This is a wonderful and fulfilling lifelong practice if you can avoid psyching yourself out before you get rolling!

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If you have an iOS device tons of free or cheap music creation apps are available. Korg Gadget is only $30, but is more than enough to get started. You can even plug in an audio interface and record straight into it.

You have standalone devices, like the Akai MPC. Literally just load in some 8-bit samples and start playing around, this tends to be a bit of an investment though as the standalone devices start at like $700.

My personal suggestion, assuming you have the money to spend would be to buy something like Maschine, 200$. Install a Chip Tune VST.

https://www.sweetwater.com/store/detail/MaschMik3--native-in...

However that's just me speaking from producing primarily hip hop, trip hop, and lo-fi beats.

Since you mention rock like four times, obvious answer is you should go and buy a guitar and maybe take some classes.

If you spend at least an hour each day on focused learning and practice, you could probably be writing basic music in a year.

Pianote.com is where I got started, but now I’m learning on my own.

Also learn to transcribe melodies by ear as you go. Start with Happy Birthday and keep practicing.

Based on your interests I would highly recommend buying a cheap electric guitar and plugging it into GarageBand to emulate amps and effects pedals. Learn some power chords and explore the effects. You'll be making music within 15 minutes.

Please, please don't make your own music software in C until later in this process or else you'll spend most of your time not making music.