The following ideas tend to occur out of nowhere during actual project design and constructions. So as to not lose sight of such ideas, I scribble them down in the moment.
Quartertone Marimba (Concept)
Rather than using two marimbas, with one tuned a quarter-step sharp-of-pitch above the primary marimba, my thinking was to create an inclusive configuration where all quartertones could fit within a single frame.
Quarter Step Layout Logic
Below shows a strategy with three views (top, front, and side) of a single octave of notes. The idea was to place the quartertone notes in-between the naturals and the accidentals rows. Just like the half-step sharp symbol (#) (which in this case equals two-quarter sharps) is added to the accidentals in a standard chromatic instrument, a single-quarter-sharp symbol and a three-quarter-sharp symbol would be applied to the center row of notes. See the top view illustration (to the far left) which shows how the symbols look and are applied to the appropriate quarter-step notes.
Since C & D, D & E, F & G, G & A, and A & B are full-steps, there needs to be three quarter steps placed between them. Since the E & F, and B & C are already half-steps, a single quarter-step is placed between them.
Note: This layout may not easily facilitate a "super" chromatic run of notes.
Below (L) shows top view of a two-octave version (R) lists the bar sizing for a three-octave instrument
Intervallic Marimba (Concept)
The design and construction of an "Intervallic" (Interval-related) marimba. An instrument that can be played on both sides simultaneously. This instrument has to directional modes: from one direction the intervals expand and from the other the diminish. The syste utilolzes note from the 12-tone equal-tempered system.
This instrument concept is based on the interval distances between notes. In one direction the first interval is the maj 7th, followed by the min 7th, then maj 6th, 6th and so forth down to the min 2nd.
In the other direction for first interval the min 2nd, followed by the 2nd, then min 3rd, 3rd, and so forth up to the maj 7th. The interval becomes the defining characteristic of the marimba.
The idea is that one direction the intervals start wide and then narrows or gets closer together. The other direction, the interval starts close and then gets wider or farther apart..
Left: Narrow intervals start in the low-end.
Middle: Narrow interval start in the high-end.
Right: This shows how both sections are attached to each other - at their low ends.
Marimba Art Sculptures (Concept)
The shape of the sculpture dictates the tonal frequency and sound. Visual shape first, tonal resonance second that results from that visual shape. The design, shape, and size are visually driven. There are four rules for these artworks:
1) Every piece has to contain resonant chamber(s) each with its own opening.
2) A vibrating bar, matching the resonant frequency, must be connected to the structure with its underside placed directly over the opening of the artwork.
3) The bar must be within easy reach as to be struck with an appropriate mallet by the attendee.
4) There can be any number of notes that the designer/sculptor desires.