I'm flattered that Robbie dug up my old posting on the Triola zither.
It's fun to watch and play.  Is it unique in being "semi-automatic",
or are there other instruments where the melody or accompaniment
(but not both) is mechanical, but the player must supply the other?
Of course, any player piano lets you add your own notes.  :-)

I have a "roller zither" that's not automatic, but works much like the
Triola.  The melody strings are played by pressing buttons (one per
note) on a carriage that sits above the strings on a pair of wooden
rollers.  Your right hand, besides pressing the note buttons, shakes
the carriage back and forth to get the reiterating effect.  Each button
has a little plectrum that plucks its string in both directions.  The
scale is not fully chromatic, having F#, G#, and C#.

This to-and-fro motion is just like the Triolas, except the player has
full control over it, including single notes or any speed of tremolo.

There is the usual set of pre-tuned chords; I think mine has five.
Six is about the most I've ever seen on a chord zither of any type.
A useful trick is to tune the A and perhaps the D chords to minor
instead of major.  I wonder if any Triola rolls were set up to be
played that way?

There were innumerable variations on zithers that were sold to
households around the turn of the century, with gadgets to ease
the playing of chords, melody, or both.  The Autoharp is well known,
as is the Ukelin, where you bow the melody strings.  And I have a piano
zither, where small keys strike the melody strings with tiny hammers.

I won't try to describe the Marxolin or Marxophone or "Hawaiian"
instruments.  You can see a parade of all these on eBay: search under
"zither."  These aren't automatic, but they do try to make music easier
to play for beginners.  Should we discuss "semi-automatic" instruments
further on this List?

Incidentally, the true Austro-German zither is totally manual, with no
pre-tuned chord sets.  It takes serious practice, and yes, three hands
would be very helpful!  The left hand picks out bass, chords, and
melody, while the right hand frets the melody notes.  "Third Hand
Theme" anyone?

Mike Knudsen