Mechanical music terminology and standard usage is an interesting
subject!  A photoplayer is by definition an instrument that was made
to accompany silent movies.

Although it might sound something like an orchestrion, the photoplayer
is not included in that category because of

- its intended use,
- its unique cabinet design (with the extra instruments in side
  cabinets that are short enough to fit under a movie screen, with
  grillwork in front of swell shutters instead of art glass),
- the hand-playable capability that was always present,
- the fact that most use organ blowers rather than orchestrion-style
  bellows pumps, and
- the fact that the rolls never operated the sound effects
  automatically (bird whistle, train whistle, Klaxon horn, auto exhaust,
  pistol shot, horses' hooves, trolley bell, doorbell, chimes, etc.).

American Fotoplayers used player piano rolls exclusively, which play
no drums or traps automatically.  All of the other companies offered
models that used orchestrion rolls (usually) and/or player piano rolls
(less commonly).

In addition to the models that use player piano rolls, Seeburg
photoplayers play either G rolls (bass drum & cymbal, tympani effect,
snare drum, triangle) or MSR or H rolls (the same drums/traps as
Seeburg G rolls plus castanets).

Small Wurlitzer photoplayers use 65-note APP rolls (bass drum & triangle,
snare drum), medium-size Wurlitzers use Mandolin PianOrchestra rolls
(same drums/traps as Seeburg H plus tambourine), and the largest use
Concert PianOrchestra rolls (same drums/traps as Mandolin
PianOrchestra).

Marquette Cremona photoplayers play 134-hole Solo S rolls (same
drums and traps as Wurlitzer Mandolin PianOrchestra).

Combination piano/organs, such as the Operators' Reproduco, Seeburg
Celesta DeLuxe, and Wurlitzer Organette, were used in theatres, but
they are considered to be neither photoplayers nor orchestrions because
they have no drums, traps or sound effects.

Further complicating matters of terminology, some of the early
nickelodeon theatres did use orchestrions instead of photoplayers.

The difference?  Orchestrions were in taller self-contained cabinets,
most had fronts decorated with art glass or mirrors instead of
grillwork, the vacuum and pressure were supplied by self-contained
bellows pumps, and almost none had controls for playing the extra
instruments by hand.  They were just put in place and turned on while
the movies played, on the premise that any music (whether coordinated
with the action on screen or not) was better than no music at all.

There are probably other subtleties that I haven't covered here, but
these are some of the main differences.  The overall subject is subject
is covered in great detail in the excellent 212-page book "Nickelodeon
Theatres and Their Music" by Q. David Bowers, originally published by
Vestal Press and frequently available from used booksellers and eBay.

Art Reblitz