The megaphallic male on the right (on the south corbel-table at Rubiães
is not sucking wine from a barrel, but playing an instrument called the dolio,
also known as a barrilete.
It is likely that this was a simple adaptation of an empty keg (rather
than a barrel)
by attaching a pipe to the bung-hole.
The motif occurs, unsurprisingly, in maritime wine-producing/exporting regions from Galicia
around the bay of Biscay to the Charente-Maritime, north of Bordeaux.
It produced a single drone-note, very like a jug from a 1920s Jug Band
in the southern USA,
and possibly was accompanied by clownish behaviour.
The word dolio is remarkably similar to dohol : a large
cylindrical, barrel-like drum with two skin heads
still played in Afghanistan, Iran and Kurdistan.
Some of the Romanesque representations of the instrument are decidedly phallic.
Other examples can be seen at
(photo by Alberto López)
Tejadilla and Castilleja de Mesleón (Segóvia)
photos by Ray Escámez Rivero
and Santa Mariña de Esposende (Ourense).
Compare the Rubiães corbel...
photos by Fernando Garcia Gil and José Antonio
...with other exhibitionist examples at Givrezac (Charente-Maritime),
at Béceleuf (Deux-Sèvres),
and at Arthous (Landes).
The left-hand side of the doorway at Moarves (Cantabria)
seems to be depicting Salomé and musicians at Herod's banquet.
see more examples at http://www.consellodacultura.org/asg/instrumentos/os-aerofonos/dolio-cabazas/
A megaphallic [c]rote-player at Santillana del Mar. The rote was an instrument
known in Wales as a crwth, sometimes played with the fingers like a lute, sometimes with a bow, and sometimes with a wheel like a hurdy-gurdy.