Doepfer A-138M

What an essential and often overlooked module! Besides its obvious use for mixing audio and CV signals, Doepfer A-138M matrix mixer can also function as a sequencer: you can turn it into a 4 step chord sequencer (4 note chords!) or a 16 step traditional sequencer by adding a few additional modules. Feed gate outs 1-4 from either A-152 or A-161 into each respective input. Send each output to 1V/Oct inputs of your 4 VCOs. Play with a clock divider to find the right pace. Or do the same, but connect outputs into an A-151 and then into a VCO. Now you've got 16 steps! As always, very impressed with Doepfer.

This unit is exceptionally useful.
As a straight forward mixer, you can mix up to four signals and route them to four separate outputs, and each output can be set independently to sum the signals in a unipolar (positive voltage only) or bi-polar (positive and negative) fashion. Leaving the first input unplugged also allows you to add an offset to each output via the top row of knobs - very useful!
Where this unit comes into its own however is as a sequencer - you can create four separate sequences from the same input voltages - which can then be used to drive four oscillators to give some nice chords, or if you add an A-151 sequential switch (recommended!) you can create much longer and more complex sequences by switching between the outputs and sending them to one oscillator.

You can also mix LFOs / envelopes etc to create interesting and evolving modulation sources.
You can even (very carefully!) feed the outputs back into the mixer and use it for 'zero-input-mixer' music (disclaimer - feedback is tricky to control! Be careful!)

The usual high Doepfer standards apply here, the perfect blend of affordability and usability.