Analogue Solutions produce a range of step sequencers.
Overview of Analogue Sequencers
Analogue sequencers allow you to program a set of voltages and Trigger events, typically 8 or 16. You can step through them by using a clock signal or LFO square wave. With each step, the next voltage as set by the control is present at the CV output. This way repeating melodic lines can be produced. The sequencer need not control pitch, it could be used to change the filter cut-off, volume, or LFO speed.
The advantage analogue sequencers have over hardware sequencers is firstly their immediacy. Having all the controls, switches and sockets in front of you allows quicker programming. Secondly, as the output is an analogue control voltage and not a digital MIDI signal, the output of analogue sequencers can easily be mixed with other voltages, or processed in some way.
You are forced to create melodies or sound loops in a completely different way to entering notes into software. This different approach will give you results you could never get with software. Happy accidents also, and a more rewarding way to create music.