COMPUTER
It's kind of obvious that if you're going to be working with electronic music that you need to buy a computer. I'm a computer technician, so I can suggest a lot of different things, but I don't want to get overly detailed.
For purposes of these articles, I'm primarily going to be talking about and using a Windows 8.1-based PC. Without getting overly detailed, the main reason that you'll want to use a PC over a Macintosh, iPad/iPhone, Android device, or Linux box is because there is an awful lot more free music software available for Windows. The secondary reason is that you'll get more performance for the money. As I mentioned earlier, I want to get as close to free as possible. However, if you've already got something other than a Windows-based PC, some of the software I'll mention may have an equivalent for your device and, for Linux users, you might be able to run some of the software through WINE.
Allow me one geeky comment: there is a really interesting piece of software available for the Microsoft Surface Pro called StaffPad. It's a piece of software that allows you to use the Surface Pro's digitizer pen to hand-write notes on the screen and it converts what you wrote into a variety of formats. If I didn't already have a PC, I'd definitely consider this a reason to look at the Surface Pro.
At bare minimum, you'll need:
Intel Core 2 Duo (not "Core Solo")
8gb RAM
128gb Hard disk
Display capable of at least 1280px x 720px (aka "720p"). You can also read that as "most displays."
Windows 7 64-bit
This is quite inexpensive. You can pick up a used used Dell E6400 laptop for around $150. If you look around a bit, you might be able to pick up on even better deals, like a used i7-powered Dell E6420 for $300.
I understand that it's a bit difficult to tell which computer is better than another. There are lots and lots of variables that will affect computer performance. Intel hasn't helped: they've had i7 processors around since 2010 and, of course, a 2010 i7 is slower than a 2015 i7. If you go by raw processing speed and assume that the machines you're comparing have the same amount of RAM, same kind of hard disk, and same kind of video, if you can find out the name of the computer's processor, you can use a benchmark chart to tell you what's fastest.
You may have wondered why I just mentioned laptops. The main reason is because you don't have to buy a separate monitor, thus you'll keep the cost down a bit. However, provided all other components are equal, a desktop computer can have a faster processor at a lower price. Another way of looking at it is that I couldn't build you a desktop computer that has the same specs as that Dell E6420 I mentioned for $300.
I also want to mention that a lot of the free software I've tried requires you to have an "ASIO-compatible sound card." Most sound cards are or can use a free driver. However, if you're going for performance, you might want to check out Amazon and buy a dedicated card. A PC-card based sound card is about $14 and a desktop sound card is about $26 new. This is a PC-only thing. Macs don't need it.
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MIDI KEYBOARD
If you really want to get technical, you don't really need to get a MIDI-capable keyboard. However, you've made your life a lot more difficult. You'll have to point and click to edit notes and that's really not fun. Fortunately, MIDI-capable keyboards aren't that expensive. I'd also recommend that you get one that can use a sustain pedal: one of the input methods in some notation software has you play notes on a MIDI controller while you tap out the beat on the sustain pedal or using a specific key on a keyboard controller. I've never used that feature much because I'm not a keyboard player, but it can be a really fast way of entering notes.
The cheapest keyboard controller on Amazon is the 49 key Alesis for $80 new and $65 used. You can get an 88-key controller for about $170, used. I've got an old Yamaha PSR-175 that my wife hasn't used in a few years, so I didn't need to buy anything.
Before I leave the topic, I should mention that you'd probably want a keyboard that has a minimum of 49 keys. Smaller keyboards generally have a button or two that will allow you to play an octave or more higher or lower, but if you're playing a piano part, the 25-key devices get really annoying really quickly. Also note that we really don't care about the sound quality of the keyboard because we're just going to be using it for note entry and editing.
============
MIDI INTERFACE
You have to get the keyboard to talk to the computer and vice-versa. For that you need a MIDI interface.
There are hundreds of brands of MIDI interfaces. I bought this one because I can use it with my iPad 3, PC, and Mac. It's $30 new, $24 used. If you just want to use one kind of device, there are cheaper ones. The cheapest one I found was this one for all of $8. Just browse the Amazon Best Sellers list. You might even consider the IK Multimedia iRig 37-key controller with built in MIDI interface and cables for $70, used.
============
Let's total up the purchases, using the lowest prices:
Computer: Dell E6400 Core 2 Duo, 8gb RAM, 128gb hard drive: $150
Keyboard: Alesis 49-key controller: $65
MIDI Interface: AY03 MIDI Interface: $8
Optional: Dedicated ASIO-compatible sound card: $14
TOTAL: $223 ($237 with sound card)
It's kind of obvious that if you're going to be working with electronic music that you need to buy a computer. I'm a computer technician, so I can suggest a lot of different things, but I don't want to get overly detailed.
For purposes of these articles, I'm primarily going to be talking about and using a Windows 8.1-based PC. Without getting overly detailed, the main reason that you'll want to use a PC over a Macintosh, iPad/iPhone, Android device, or Linux box is because there is an awful lot more free music software available for Windows. The secondary reason is that you'll get more performance for the money. As I mentioned earlier, I want to get as close to free as possible. However, if you've already got something other than a Windows-based PC, some of the software I'll mention may have an equivalent for your device and, for Linux users, you might be able to run some of the software through WINE.
Allow me one geeky comment: there is a really interesting piece of software available for the Microsoft Surface Pro called StaffPad. It's a piece of software that allows you to use the Surface Pro's digitizer pen to hand-write notes on the screen and it converts what you wrote into a variety of formats. If I didn't already have a PC, I'd definitely consider this a reason to look at the Surface Pro.
At bare minimum, you'll need:
Intel Core 2 Duo (not "Core Solo")
8gb RAM
128gb Hard disk
Display capable of at least 1280px x 720px (aka "720p"). You can also read that as "most displays."
Windows 7 64-bit
This is quite inexpensive. You can pick up a used used Dell E6400 laptop for around $150. If you look around a bit, you might be able to pick up on even better deals, like a used i7-powered Dell E6420 for $300.
I understand that it's a bit difficult to tell which computer is better than another. There are lots and lots of variables that will affect computer performance. Intel hasn't helped: they've had i7 processors around since 2010 and, of course, a 2010 i7 is slower than a 2015 i7. If you go by raw processing speed and assume that the machines you're comparing have the same amount of RAM, same kind of hard disk, and same kind of video, if you can find out the name of the computer's processor, you can use a benchmark chart to tell you what's fastest.
You may have wondered why I just mentioned laptops. The main reason is because you don't have to buy a separate monitor, thus you'll keep the cost down a bit. However, provided all other components are equal, a desktop computer can have a faster processor at a lower price. Another way of looking at it is that I couldn't build you a desktop computer that has the same specs as that Dell E6420 I mentioned for $300.
I also want to mention that a lot of the free software I've tried requires you to have an "ASIO-compatible sound card." Most sound cards are or can use a free driver. However, if you're going for performance, you might want to check out Amazon and buy a dedicated card. A PC-card based sound card is about $14 and a desktop sound card is about $26 new. This is a PC-only thing. Macs don't need it.
============
MIDI KEYBOARD
If you really want to get technical, you don't really need to get a MIDI-capable keyboard. However, you've made your life a lot more difficult. You'll have to point and click to edit notes and that's really not fun. Fortunately, MIDI-capable keyboards aren't that expensive. I'd also recommend that you get one that can use a sustain pedal: one of the input methods in some notation software has you play notes on a MIDI controller while you tap out the beat on the sustain pedal or using a specific key on a keyboard controller. I've never used that feature much because I'm not a keyboard player, but it can be a really fast way of entering notes.
The cheapest keyboard controller on Amazon is the 49 key Alesis for $80 new and $65 used. You can get an 88-key controller for about $170, used. I've got an old Yamaha PSR-175 that my wife hasn't used in a few years, so I didn't need to buy anything.
Before I leave the topic, I should mention that you'd probably want a keyboard that has a minimum of 49 keys. Smaller keyboards generally have a button or two that will allow you to play an octave or more higher or lower, but if you're playing a piano part, the 25-key devices get really annoying really quickly. Also note that we really don't care about the sound quality of the keyboard because we're just going to be using it for note entry and editing.
============
MIDI INTERFACE
You have to get the keyboard to talk to the computer and vice-versa. For that you need a MIDI interface.
There are hundreds of brands of MIDI interfaces. I bought this one because I can use it with my iPad 3, PC, and Mac. It's $30 new, $24 used. If you just want to use one kind of device, there are cheaper ones. The cheapest one I found was this one for all of $8. Just browse the Amazon Best Sellers list. You might even consider the IK Multimedia iRig 37-key controller with built in MIDI interface and cables for $70, used.
============
Let's total up the purchases, using the lowest prices:
Computer: Dell E6400 Core 2 Duo, 8gb RAM, 128gb hard drive: $150
Keyboard: Alesis 49-key controller: $65
MIDI Interface: AY03 MIDI Interface: $8
Optional: Dedicated ASIO-compatible sound card: $14
TOTAL: $223 ($237 with sound card)