DIN Sync has introduced the ModSeq kit, a DIY minimal 8-step sequencer for Eurorack modular synthesizers.  

Here’s what they have to say about it:

The ModSeq is a low cost, low HP, 8 step auxiliary sequencer. Its primary duty is for modulation, however it will function perfectly well as a note sequencer, too.

Since the ModSeq has only 4 knobs but 8 steps, steps 5-8 share the knobs of steps 1-4 but in a mirrored fashion. The result of this is somewhat akin to a sample and hold circuit, but programmable rather than random.

Here’s a demo of the ModSeq in action:

The price of a kit is 550 SEK including VAT (about US $75). See the DIN Sync site for more info.