I choose the PC for this topic as I have always been using PCs. Most people tend to stick to what they know best, for me it is the PC. I do understand the MACs initially had better interfaces for MIDI which is why developers made software exclusively for the MAC. e.g. Logic Pro. Nowadays it is just as easy to connect MIDI to a PC as it is for a MAC.
Do I need a monster PC?
You do not need a power PC to in order to make music. However the more tracks you have going simultaneously, then more demand on the CPU.
Type of CPU
A Celeron can easily handle most home made projects as long as you don’t have too many VST plugins running at the same time. A Core i3 will be able to handle and bunch of plugins. But your safest bet would be a Core i5 to handle the really heavy VST plugins. Core i7 is probably overkill.
For Audio processing only, there is not much demand on the CPU anyway and a Celeron processor can handle multiple tracks and effects. One of my laptops is a Celeron I have had up to 10 tracks running at the same time. Multiple effects too, and the CPU usage percentage barely went over 15%
However a slow CPU may mean higher latency. Latency meaning the delay from when you press a key on a MIDI device to hearing it from the speaker.
For home studio work, the recent standard of 8GB RAM is more than enough. Even games don’t use up all of 8GB RAM.
Hard disk space is never usually an issue either. Most systems come with 500GB minimum. External Hard Drive and Cloud back up are relatively inexpensive nowadays.
This is what takes a lot of processing power from your PC. The built in sound card in your PCs motherboard will not normally be adequate for music production. You will need a decent Audio Interface which is connection via either USB or Firewire. The latter having a slightly faster connection due to to a high bandwidth.
An Audio Interface will also almost zero latency when monitoring input. Essential for singers who need to hear their own voice.
Audio Interfaces can be purchased from around $100 and can go up to around the $1,000 mark.
Even if you don’t play the keys, you will need at least one MIDI input controller. Since they do not contain any on-board sounds, they are relatively cheap. A very popular MIDI controller keyboard such as the M-Audio Oxygen 49 can be purchased for around $150. They are normally used to trigger VST sounds within your DAW.
Software / DAW
This is where most of your work is going to be done. Therefore it is best to try different software / DAW and find one which suits you the best.
Software can range from $100 up to around $500. Do also note that there is also free software such as Reaper.
Also note that as well as the DAW. You may need to purchase some good VSTs. These are instruments pluggins that are compatible with all DAWs (expect for “Reason” which has it’s own refill type pluggins). I tend to use lounge lizard a lot, a very good epiano pluggin.