Connect a MIDI controller keyboard to your PC. Some controllers connect seamlessly using USB, while others will require you to connect using a MIDI cable and a MIDI USB adapter. MIDI controllers allow you to record custom loops using Cubase's virtual instruments. If you do not have access to a MIDI controller, proceed to the next step. You can still create loops using a step sequencing method.
Open your Cubase software. To create a new song project, select (File > New) on your menu bar.
Click (Project > Add Track > MIDI) on your menu bar to create a MIDI track. Each layer of audio that you wish to incorporate in your loop (such as bass, keyboards and percussion) will require the use of its own "track," which looks like a long horizontal space on your main window.
Select a virtual instrument for your track. Click the track name (which should read "Track 1") in the left column of your main window to highlight the track, and then select (Devices > VST Instruments) on your menu bar. From the subsequent list, choose a software synthesizer and select a sound preset, such as bass line, synth pad or techno kit.
Click the circular "Record" button and begin playing your MIDI keyboard. The notes that you play on your keyboard will transmit to Cubase using your selected virtual instrument sound. Press "Stop" when you finish recording. If you do not have a MIDI keyboard, use your mouse to highlight a designated number of bars on your horizontal track (the number of bars you will need for your recording). Double-click the highlighted space to open the piano roll then insert notes manually by clicking the squares on the grid (high squares correspond to high notes and low squares correspond to low notes).
Create a second track then designate a virtual instrument to it as you did in Step 4. For example, if you recorded a drum pattern for your first track, you might select a bass setting for your second track, for a layered drum and bass arrangement. Repeat this process for as many instruments as you will need to complete your loop.
Export your finished loop as an audio file. Select (File > Export > Audio Mixdown) on your menu bar, enter a name for your loop and choose an audio format. Finally click "Export" and wait as Cubase converts your project into a self-contained audio file.