Having had something to do with a pianist who had a 7/8 keyboard, and having visited Mr. Steinbuhler in his factory, I feel a certain sadness about this. Physics, biology and economics are unbending. Clothing and shoes can be easily made in many sizes. Stairs tend to be one size and good luck to all. When I look at the bass section of the orchestra, folks tend to be an appropriate size for the instrument. Instruments converge toward a design, and when you pull away from that, things become difficult, and expensive.
I have never seen a staircase that adjusts to the size of the people using it. I do notice that the depth and width of tread does vary around here, the most comfortable to use being staircases built before 1900.
As far as double basses are concerned, they do indeed come in various sizes, though instruments like trombones, flutes, etc, are inflexible as the dimensions have a fixed relationship to the pitches.
Although keyboards can be made with a shorter octave span, and indeed this measurement varies between French and Italian style instruments, I dont think a standard instrument is a problem for a child, who naturally has an inability to stretch wide intervals until his or her hands are fully grown. Even though the keyboard octave span can be made as narrow as you want, since the keys are levers, the distance between strings is less negotiable in order to be able to fit the jacks in.
David
There was a math professor at the local university who was blind. He mostly coped very well, he even worked out a way to mow the lawn at his house. But the university built a new campus and hired a famous architect (named Paul Rudolph) who go tit in his head to make the staircases all different. the treads were wide and low and they snaked all over the place. And it took the math professor a couple of years to learn the quirks of all of them so he could get from office to classroom to cafeteria on his own without falling down.
Likewise, I think it would be very hard to play say Scarlatti’s cross-hands pieces on somebody else’s harpsichord if there wasn’t a standard distance from the bass to the treble. (But somebody probably already said that)
Judy (busy trying to learn the piano part to a symphonic medley from the movie ‘Frozen’ for what purports to be a holiday concert. I showed up for the one rehearsal unprepared, because it all looked like filler to me, and it turned out to be vitally important thematic material which I am soloing on. Sigh. happy holidays)
Domenico Statuto said, " I admit you can’t play octaves at 6-10 yo, though."
I would disagree. I began piano at around 10—with a much wider keyboard octave than many harpsichords—and don’t recall any difficulty playing octaves.
Ray