Connect a USB or Firewire cable, depending on make and model, to the "Output" port on the rear of your audio interface. Connect the other end to a relevant port on the side or back of your computer. The audio interface serves a similar function to a studio mixing desk, but converts the audio to data so the digital audio workstation can interpret it.
Connect the MIDI controller to the computer with a USB cable.
Plug a 1/4-inch jack cable into an electric guitar. Plug the other end into the "Instrument Input" jack on the front of the audio interface.
Open your preferred digital audio workstation. If one doesn't open automatically, click "File" and select "New Session."
Click "File" and select "New Audio Channel." Name the channel "Guitar 1."
Select a tempo. For your music to sound spacey, a slower tempo is in order. For example, Pink Floyd's most hypnotic and spacey songs, like "Us and Them," were characterized by a slow tempo. The default tempo in typical digital audio workstations is 120 beats per minute, or BPM. Set yours to around 100 BPM.
Play the guitar as loud as you intend to record. If the volume units meter on the recording interface flashes red, the gain is too high and will distort. Turn down the gain dial on the audio interface. Aim for a level that is as loud as can be before distortion.
Hit "Record" and play your take. Once you're happy with it, open a second channel, call it "Guitar 2" and record an identical take. This creates a stereo pair. One distinctive characteristic of stereo guitar is natural phasing, with creates a spacious sound.
Click "Effects" and select "Reverb." Turn the "Depth" parameter up to around 70 percent. Reverb adds ambiance to audio. It is similar to an echo, but more subtle and gentle. Click on "Guitar 1" and add the same reverb effect.
Click "File" and select "New MIDI Channel." MIDI is distinct from audio in that you can use software instruments to access sounds that would otherwise be difficult to record in the home studio. Click "Instruments" and browse for a theremin. Use your MIDI controller to record a theremin track over the guitar to create a sci-fi-spacey vibe.
Connect the female end of an XLR cable to the bottom of a microphone. Connect the other end of the microphone to the XLR input jack on the front of your audio interface.
Open two audio channels, name them "Vocal 1" and "Vocal 2." Record a stereo take and add reverb, as you did with guitar.