working with multi-track single wav files on Reaper and creating 'minus' tracks

To split a single multitrack file into separate mono tracks in Reaper (at least in Reaper 5), menu item
Item -> Item processing -> Explode multichannel item to one channel items

Then, single tracks can be solo'd till we hear only music, if the narration track is localized to one or two tracks. Muting does not seem to work, but solo seems to work. Then the file can be rendered into a 'minus' track, without the narrator.