MIDI out from freeware sequencer to PD or Max/MSP
Max/MSP has the midiparse object which is incredibly useful for handling midi data. Midi Ox is a program that will help you with routing occasionally. As far as freeware, you get what you pay for. Hydrogen is an open source a drum machine that will send midi out. You'll just to configure Max or Pd to receive the channel you're sending out of your sequencer.