more than one job
So it is OK to ask employees to do more than one job for the same employer, but not for separate employers.
Although that's not true either, when I worked for two sister companies I actually worked for two employers, although only paid by one.
As financial difficulties have multiplied most people find themselves doing three or more jobs as their team is reduced by cutbacks.
Finally continually being asked to do more with less has an end point when we have to do everything with nothing - our team is almost there.