For the digital part i chose to use atmega8 microcontroller to do all the tasks related to the sequencer control. These are mainly handling the buttons (start, stop, running mode, load/save pattern etc.), controlling the led's and generating the trigger pulses and accent switches to control the analog sound modules. When starting i thought that one atmega8 will be sufficient to do all the task but i soon realized that i needed a second one.
I decided to split the two controllers into a 'master' controller and a slave controller. The idea behind this is that the master processes all the incoming information (buttons and sequencer clock) and the slave controller is used to control the output (the leds and interface to soundmodules). Communication between master and slave is done via i2c.
Here is the schematic (not tested yet) for the master partHere is the one for the slave part