Musonda is on the books of Orlando Pirates, having spent last term on loan at Golden Arrows.
Cale is a free agent after parting ways with Ajax Cape Town in the off-season.
Both players are training with the PSL newcomers with a view to impressing coach Allan Freese.
"The players are here but at the moment I can't say if we would sign them or not," Freese tells snl24.com/kickoff.
Highlands have been busy in the transfer market, notably bringing in Golden Boot holder Collins Mbesuma, fellow forward Charlton Mashumba and midfielders Thanduyise Khuboni and Eddie Ngalo.