We had a toy piano in the house where I grew up. It was small, maybe 20 keys (12 white, 8 black would be my guess), made of wood, the top painted light blue, the rest of the body unpainted, no legs, about 14 inches square, four deep. Probably it dated from the late 50s. Googling around, I couldn't find an image that approximated it though I imagine the particular model wasn't uncommon around the time.
It's salient point, however, was the open nether end of the instrument. Emerging from the darkness of the box's interior were 20 or so metal rods, the ends within easy plucking distance. Perhaps they were regularly arrayed when the piano was new, but my memory of them was of a more ragtag arrangement, the 1/8" or less diameter steel dowels standing at various angles from the perpendicular.
Needless to say, fiddling with them from that end of things produced far more satisfying sounds than playing the keyboard. Flicking the rods with your fingernails generated much richer thwangs than pressing a key. Plus, you could vary the attack from hypersoft to forceful enough to set the rods vibrating against themselves or the wood casing. I created quite a ruckus over the years on a fairly regular basis as the piano was kept in a kid's/games closet in the family room, within easy reach of the TV seats. The memory of playing it is one of those that seems far more recent than it possibly could have been; it comes through very strongly. I moved to NYC in '76, so it's certainly possible I was futzing around with it after having heard experimental music of various kinds and maybe made some connection. Wonder if it's still around.
This all came back into current memory yesterday when I received a new 10" vinyl from Crouton Music, Hal Rammel's "Like Water Tightly Wound" on which he plays the instrument illustrated above, essentially a large number of metal rods, saw blades, etc., growing from a resonant wooden palette. He mentions in his notes that he wasn't very interested in setting the pieces in any kind of mathemtaical relationship, simple or complex, but instead positioning them more or less randomly. This serves to endow the music with a looser feel, of someone idly strumming through the stalks, finding a rough melody here, abstract noise there. Essentially, the result is a much better version of what I used to do; it succeeds in evoking nostalgic memories as well as providing some immersive music. A lovely little surprise.