Exporting voices as separate MIDI tracks

For example for choirs or when writing horns as voices on a single staff: how is it possible to export to MIDI and have each voice appear as a separate track subsequently in the sequencer (e.g. Sonar)?
Actually a function that would do it entirely in Notion (multi-voices staff to multiple single-voice staves) would even better as one then could always export to MIDI if needed.
Actually a function that would do it entirely in Notion (multi-voices staff to multiple single-voice staves) would even better as one then could always export to MIDI if needed.