Making drum patterns and basslines for your songs requires precise timing and each note has to be on beat so it is important to use the right tools to make it happen. A step sequencer can help with this and I will explain what a step sequencer is and how to use it to make your drum patterns and basslines.
A step sequencer allows you to turn notes on and off as the song plays along a time line made up of steps. The main use for a step sequencer is for drum patterns but they can also be used to bass and other synth patterns. Step sequencers are available as software which can be used to make patterns using a computer. There are also are also many hardware step sequencers available allowing you to create beats and sequences to sent to other midi hardware or your DAW software.
Every sound or musical note in the step sequencer software is represented by it's own row in the editor and each step in the sequence is represented by a column. The sounds are from a sound library which can be downloaded or in the case of a VST plugin the sounds could be any soft synth or sampler plugin you have loaded in your DAW software.
Below is an diagram of a step sequencer that comes included with Sonar by Cakewalk.
Some of the popular DAW software has a step sequencer included. When you want to create beats with a standalone sequencer application you can use a step sequencer that runs independently of a DAW such as BeatLines 2.
When you prefer the hands on approach to making music then a hardware sequencer is what you are looking for. A hardware step sequencer will connect to your computer and other MIDI devices then pass the not on and off information to them. Hardware sequencers can be set up as a MIDI controller for your DAW the same way your MIDI keyboard is set up and will send the MIDI instructions to the DAW for processing.
I have introduced you the two types of step sequencers that you can use but there is an emerging trend to use a bundle which includes software and hardware to make beats and grooves. The sequencer is part of the software while the hardware will offer control of the software to offer an integrated solution to enhance your creative experience.
A popular choice in this area is the Native Instruments Maschine which consist of a hardware controller with software which work together to quickly make beats, bass lines and other music.