Sonar does not support sending midi clock (bars/beats/tempo, not midi timecode) to multiple outputs. Therefore, to route the midi clock signal to multiple devices, the devices must have a midi thru port (this simply passes the IN signal to the THRU). Hookup the first sequencer's in to the out of the midi interface, and the out of the sequencer to the in of the midi interface. The second sequencer's in should be hooked to the first sequencer's THRU, and the output to the midi interface's IN on another port. Continue this for your other sequencers.