If you're mostly into making soundtrack music for games, movies, trailers and so on, it's important that you know how the computer specs need to differ from other music production genres. While producers in all the different fields of music work in the same sort of digital environment, you as a soundtrack composer, need primarily to beefen up on two things:
You need more RAM because you are working primarily with a lot of heavy, large size sample libraries, that need to have enough space to sit in your random access memory when you're composing. RAM is so important to not skimp out on because you will find when you are working with orchestral samples, the RAM quickly reaches its limits.
I started out on 8GB of RAM when I first started making professional music many years back, and I quickly found out that it was too little. So I upgraded to 16GB and I felt it did so much for how I composed – a great deal of improvement and freedom. You don't need to be as limited in what you load up into your RAM anymore if you have enough space to it - no need to cut corners.
If you really want to feel freedom with how much you can load up in your projects, and increase the size of your projects dramatically, you should aim for 32GB - 64GB of RAM. This amount of RAM is just ace and you'll never feel longing for more!
And for the same reason, more disk storage is preferable for soundtrack composers because the sample libraries are so big. Some libraries are over 100GB and when you have tens of libraries, you can quickly reach the size of your hard drive.
You want to have fast drives because you are streaming a lot of samples. Load up times can drastically increase with slow drives. If you are loading up samples with the sampler Play from EWQL, it might take minutes to load up with a mechanical drive, while it can take literally a few seconds with an SSD. The same thing applies to Native Instruments' Kontakt.
The very best and fastest drives are of course SSDs, but they are also more pricy.
If you're on a portable studio, you'd want to get at least USB3 as your connection. Thunderbolt + SSD as external drives is the very best way to go, but it is also among the most expensive ways. I manage fine on my Rugged Mini 2TB USB3 for my portable setup.
The CPU is your processing unit, it is what calculates everything that needs calculating. In music terms, this means all your digital audio processing and program performance. You should not have too slow of a CPU as that might cause a bottleneck in your workflow.
While it isn't as important to max out on as RAM and disk speeds (and storage) because you're not working with super heavy synths, processors and so on (although to some extent you do, but not as much as electronica and EDM producers for example), you will feel an overall boost in performance if you beefen up on the CPU as well. I would recommend getting at least 3GHz quad for stationary as a minimum, and 2.5Ghz quad for laptops. Preferably what I've noticed on computers is that you'd want to have 3.5Ghz for stationary and 2.7Ghz for laptops.
Also, CPU's rarely max out unless you're really putting them under the test such as throwing around algorithmic reverbs left and right in your project. The bottleneck is usually the RAM actually.
So definitely don't skimp out on these three things! They are your priority for music production.
So then, which operating system and computer should you have for music production? The answer is really simple - any one of the two. They are both amazing computer systems, and you will find that half of the top professionals in the music industry are using Mac, and the other half Windows.
I am actually using a PC as my main rig, and while I'm traveling, I have a Macbook Pro. The Macbook Pro is an amazing laptop for music production, and I have not had any issues at all with it – up to the point where I'm favoring working on the laptop, even when I'm home by my studio.
You can use VST instruments and plugins on both operating systems, the best DAWs out there have both Mac and Windows versions, and they actually have the same things under the hood. I've been an avid fan and user of PC and Windows my entire life, and when I got a Macbook Pro for my portable studio, I found that the more I'm using it, the more I get convinced to get a Mac for my main rig too. But really, both of them are amazing computers and it's all about personal preference and experimenting – you can't go wrong with either one of them.
However, for portable studios, I would highly recommend getting a Macbook Pro. With laptops specifically, Macbook Pros are incredibly solid, powerful, slim and easy to use. Get one with at least 8GB of RAM, 2.2 GHz CPU and 512GB SSD (preferably 16GB RAM because you will fill up 8GB quite fast). I've used Windows laptops as well for portable solutions, but find that Macbook Pro beats them on all corners. But again, it's all about personal preference and experience!
On my main rig, I'm using a stationary PC with:
My stationary computer setup is a very powerful home studio that is very good for any music production, and I can produce almost anything on it. I have created full orchestral film and game scores on it, trailer music, and tons more. I use two monitor screens because it allows me to have many more windows open and drag my mixing console to one monitor, and have the sequencer on the other.
You don't need this powerful of a computer, and I prove that by having a less powerful laptop and can pull off almost everything I can on the stationary one. But RAM and SSD storage is very important to have enough of! The processor will decide how much processing and plugins you can run at the same time, so that is also important for more demanding projects.
For the music I do (mainly films/games/trailers/personal soundtrack music), I don't use microphone all that often. I do sing and record my own instruments (such as trumpet and trombone, ethnic percussion, and so on), but 90-99% of my music comes from sample libraries and synthesizers.
And as explained earlier, I am using a Macbook Pro for my travels (currently a mid-2014 15" retina model), and do just fine without an audio interface. All I need is the laptop and a 25 key MIDI keyboard for 95% of my music projects.
All you really need is actually the computer. I mean, you don’t have to get a MIDI keyboard or an external sound card (even if I would highly recommend, even urge you to get a MIDI keyboard) to get started writing music digitally. All you need is a computer and some way to hear what’s coming out of it. But to be efficient, have fun and really get that music flowing, having a MIDI keyboard will be invaluable - and an external sound card for some better audio drivers and input for microphones, guitar cables, and so on.
If you do get an SSD in your storage, which I indisputably recommend (if it’s in your budget), be sure to install the most important software on it. This includes your OS, your DAW, and other programs that you need to function fast and efficiently. You can also put important and often-used samples on it for fast streaming.