For a long time, I happily downloaded Terry Smythe's excellent MIDI 
files he made from scans of player piano rolls.  When my PC began to
get flaky and I started relying on a Mac, I searched in vain for a
program as wondrous as VanBasco's Karaoke Player, which was (and is)
just for PCs -- you lucky PC people!

Today, I finally found something that can fill the gap for me without
my having to fire up my ailing Vaio.  "Midi Sheet Music" shows music
staffs (I'm seeing five just now) and a piano keyboard that lets you
see the notes being played.  There's no piano roll view, alas, nor
lyrics view (for the karaoke folks), and it's different in other ways
as well.

It's free, though, handsome to look at, and offers some different piano
sounds to listen to.  It plays 'orchestral' MIDIs with their sounds
intact, too, if that's what you have.  It also has an Android version
so I can listen to piano rolls on my phone.  It may well have versions
for other platforms; I just looked for the ones I knew I'd be using.

To be sure, nothing can replace the joy of watching a real player piano
(or other mechanical instrument) doing its thing live and in person.
Sometimes, we settle for a next-best option that fits in a shirt
pocket.

Kip Williams
Pittsford, New York