As one of Vuo's developers, I work on Vuo's engine (the thing that makes compositions run), work on nodes, and write documentation. You'll see me on the forums answering people's questions about Vuo.
I've been developing apps and frameworks for several years (since I was in college). Pre-Vuo projects include Kineme Quartz Composer plugins, iOS apps for education, an app that analyzes photographs of tomato slices, and software to help people with disabilities use talking keyboards.
I enjoy using Vuo to make live music visuals. My hope for Vuo is that it will grow into a community of people of diverse backgrounds and identities making lots of different artistic, useful, unique, goofy, beautiful, crafty, wonderful compositions.
You can nearly do the coloring with Make Vertex Attribute Shader. You end up with one corner black instead of a chosen color. I wonder if you could fake it with some color adjustments (Render Scene to Image and then modify the image).
By "rotating about an arbitrary axis", do you mean the edge of the triangle? That's quite doable using transforms.
Pitch detection is an interesting and difficult problem :) The way that brains perceive sound is weird, and not always what you would expect from looking at an FFT. A sample FFT of a clarinet and a trumpet are here (p. 125-126).
Rather than trying to tackle the whole MIDI range, I'd recommend starting with an octave or less, and see how that goes. Like, if you know the note being played is somewhere within that octave, does the highest-amplitude frequency within that octave correctly detect the note?
In your composition, I'm suspicious that maybe Split Audio by Frequency doesn't know what to do with all those zeroes. It might be assuming the input will be a list of positive, increasing numbers.
With further investigation, we discovered that the problem is in the graphics driver for the Intel HD Graphics 3000. It affects any node that uses a geometry shader (Divide 3D Object, Explode 3D Object, Facet 3D Object, Quantize 3D Object, Spike 3D Object, Trim 3D Object, Make Wireframe Shader), and it affects rendering point and line meshes.
We reported the problem to Apple, through both their Developer Technical Support and a bug report. Unfortunately, they said they're not going to fix it and they don't have a viable workaround.