hi so I am a complete beginner and I wanna buy a midi keyboard because its cheaper than a normal electric piano. I have a question I don't have a computer now, can i play a midi keyboard without a computer but only with a audio interface and headphones if not what is required to play my midi keyboard without a computer (as cheap as possible) thanks
No, a MIDI keyboard on its own makes no sound. Usually these are called MIDI “controllers”. These days, MIDI controllers are generally designed to work well with computers and specifically certain software packages. For example, the Arturia KeyLab controllers work especially well with the Arturia software synthesizer apps, and will also integrate with other popular software like Ableton Live and ProTools.
All a MIDI controller does is generate MIDI signals. You can’t listen to MIDI, it’s not sound. MIDI is sort of like the computer equivalent of sheet music: it’s just a bunch of note data that has not been turned into sound yet.
To turn MIDI into music, you need one or more MIDI sound modules. A sound module is anything that accepts MIDI data and plays sounds based on that MIDI data. There are many physical boxes that are MIDI sound modules, and computers can have software installed that make them into sound modules also.
The cheapest way to have a keyboard that makes sound is buying an all-in-one keyboard and sound module. There are several options for affordable synthesizers and digital pianos that are less than the midrange MIDI controller and don’t require a computer or anything else. One note: a lot of musical equipment does require a separate amplifier or headphones to be able to hear the audio.
Your best course of action might be to see what you’ve got saved up, establish a budget, and then go to a reputable music retailer and explain what you want and your firm budget limit.
Any electric keyboard sold today will have MIDI. It will be capable of being used as a MIDI controller with something ELSE making the sound. 20 years ago the 'something' might well have been a stand-alone 'sound module'. Now it's probably going to be a computer.
If the keyboard is sold as a 'MIDI controller', that's very likely ALL it does. As you talk of wanting something 'cheaper than an electric piano', that's probably the sort of keyboard you're thinking of getting.
But a 'piano' has 88 notes, weighted keys... There are smaller, lighter, cheaper keyboards than that which still have onboard sounds and even internal speakers. You might well consider getting one of these. It all depends on what you want to do.
You don't need a computer, but you do need some sort of sound source (iPhone, iPad or other smartphone/tablet, or a standalone hardware synthesizer module that works directly with MIDI controller keyboards) that is not your MIDI controller keyboard (assuming you're buying a keyboard that doesn't come with sounds pre-loaded). For example, I sometimes use the following setup on the road:
iPhone 7 Plus running Garageband or any other music app compatible with MIDI
Akai Professional MPK 225 (MIDI controller keyboard with no pre-loaded sounds) — this is one of the more expensive controllers for its size but I got it because it comes with a lot of features I wanted (arpeggiator, drum pads, full size keys, really nice keyboard action); you can definitely go much cheaper
USB-A to USB-B cable
Apple Lightning to USB Camera Adapter (to connect the phone to the keyboard)
Insignia Universal AC Adapter (extra power for the keyboard)
Works perfectly fine, a little bit of latency maybe.