Open your preferred DAW.
Click "File" and select "Open New." Name the track for ease of future retrieval, if you don't have a name yet call it "Drum and Bass 1."
Click "File" and select "New Midi Track." Name the track "drums." By selecting MIDI as distinct from audio, you assign the connected MIDI controller or MIDI-enabled keyboard as the primary input device. MIDI is a digital protocol that lets you program and sequence notes remotely with data commands. If you don't have an external device, some programs let you use your computer keyboard as the input device. For example, if using Logic, click "Window" and select "Musical Typing" to assign the keyboard as the primary input device.
Set the tempo. Drum and bass is typically recorded at a tempo between 160 and 190 beats per minute, or "BPM." The default BPM on your DAW is 120. Click on the box in the center of the screen, at the bottom and type in your preferred BPM. You can alter it later if it feels to slow or too fast.
Open the step editor. The method for doing so varies according to the system you use, but it is typically a simple, one or two click operation. For example, if using Reason, click "Instruments" and select "Martrix." A step editor is a grid interface that lets you program MIDI instruments visually. The vertical axis represents pitch, or if programming drums it represents different drums and the horizontal axis represents time, measured in beats and bars.
Click "Instruments," "Drums" and select an electronic drum kit from the drop-down menu.
Plot a beat. Drum and bass has prominent break beats, where the emphasis is on notes three and four in the bar. Click on the row for the bass drum, in square one, two and four. Click on the snare drum row, on square three. Click on "Pattern" or "Sample," depending on what system you use and drag the drum loop onto the MIDI channel. Program a second beat pattern in the step editor and drag that onto the MIDI channel. The interface automatically lines up the drum loops. Copy over enough loops for at least three minutes of music for an authentic drum and bass backing track.
Click "File" and select "New MIDI Track." Name this track "Synth bass line."
Click "Instruments," "Synthesizers" and select a suitably dark and heavy synth sound. Use the step editor interface to sequence a synth bass line. For convenience, sequence it in sections as you did with the drums. Once finished, drag it onto the MIDI track.