Any project that produces sound mechanically or electronically — xylophones, glockenspiels, organ components, MIDI‑driven devices, or hybrid acoustic/electronic builds.
Here's an initial assembly of the instrument with its resonator box suspended between plywood boards.
The Topsy 3 design calls for an air-operated glockenspiel, with leather over air pockets to push the strikers. I just couldn't get it to work. I might try again sometime, because it's nice to save a few magnets for other projects. Here Korben Dalek is helping in the design and construction.
Here's a view of the hammer mechanisms mounted onto plywood plates and set in place in the instrument case that will become the glockenbox
Here we have the initial layout of the glockenspiel bars inside the hard case. I measured clearances, etc, made the mounting rails, and found I had enough room for two more bars! Since the driver board has 32 outs, I figured this would be perfect. I fabricated the two lower bars.
This is an early iteration of my street organ! At this point it's playable and it includes the rebuilt Thomas orchestra bells as a glockenspiel, the kid-sized bass drum, candy-can snare drum, rohr schalmei pipes as the octave pipes, and an unfinished case.
I asked AI to draw a circus wagon that could house a street organ.
I asked Coppy to design a street organ. I gave some descriptions and ideas and AI came up with this.
Here's Copilot imagining how Topsy looks.
These are the dimensions of Topsy's case.
This is a very good (and very *practical*) question, because with **small‑diameter steel tubes** the limitation is **not “can it vibrate?”**, but **whether the ear will clearly perceive the fundamental at all**.
Below I’ll give you a **clear, experience‑backed answer**, then explain *why* that limit exists so you can design confidently.
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## Short answer (design takeaway)
For **3/4" steel conduit (EMT)**, the **lowest practical note where the fundamental is clearly perceived** is:
> ✅ **C3 to D3**
> (≈ **130–147 Hz**)