This seems to be a small bug. This works well:
Text on body font.
Text on special typeface.
However, if I either remove '21pt' from
\switchtobodyfont or just change it to '22pt'
(i.e., no change from body font size) I don't
get text for the other font.
(This is not specific to pagella and chorus,
I've checked this same problem with all other
combinations I tried. I'm using latest version
in minimals, i.e., did 'sh first-setup.hs' just
half an hour ago.)