Yes Spiral still is in development, although right now I'm actually working on both SplineEQ and Photosounder at the same time!
Why would you want the other dots to become fainter? Seems like it would only make them harder to see. I made every one of them easy to see with a concentric black-white-black pattern because there might be stuff going on below the overlay that would otherwise easily drown them out visually.
What do you mean by a chord overlay? Can you give me an example of how it would work? How would you colour the chords? I didn't really specifically consider chords (I guess you mean in a guitar strumming kind of way, right?) when thinking up Spiral, just a practical way to see the notes in music, more specifically the single notes of each instrument at the same time.
The spiral representation is not that good for single-pitch note compared to a linear/exp representation
I couldn't disagree more, because you can tell what note something is without even looking at the note label just from seeing the angle, works like the hands of a clock really, whereas with a classical flat representation you have to see how it matches with a linear sequence of notes, plus you have to zoom in, viewing the 9 or 10 octaves that might be present isn't practical in that case. Plus since the harmonics line up in a familiar pattern in the spiral representation you can more easily avoid mistaking an harmonic for a separate note, you see what belongs together as a single note.
The way it works for me is that first I try to identify the key and scale used, then when I do I rotate the visualisation to have the key be on top, then I mentally visualise the scale, for instance if it's played in D minor I set the Key knob to "D top", then regardless of the key I know that the whole minor scale is found at 12 o'clock, 2, 3, 5, 7, 8 and 10 o'clock, so if I see that familiar pattern of harmonics pointing towards 5 o'clock it instantly means something to me (a perfect fourth from the root in this case).
Spiral is meant to show you everything as it is, so you might also say that other instruments distract from the instrument you're interested in, not just the voice

. I myself rarely feel bothered by voices because they move in a very different way from anything else, if anything I find it too easy to tune it out and ignore it. Actually my biggest problem is when the lead instrument and the rhythm section drown out the more subtle accompaniment. As for the loud songs you're right, though one solution is to crank up the Gamma, it makes fundamental tones stand out usually, by making things more contrasted and dimming broad noises and other less dominant parts of the spectrum. Another problem is when the song is poorly mixed in stereo (like most of everything made in the last 20 years) and that everything is centered, "stereo width" being only an effect. Then it might as well be mono, and everything ends up looking about the same colour.
Do explain your colouring ideas though, I'm open to ideas on different visualisation colouring schemes, mostly to help with mixes that are too mono or centred, and also maybe ways to make different octaves clearer, although this one isn't obvious since knowing the octave of the overtones doesn't necessarily help you identify the octave that the note actually is in very much. Also I'm thinking of changing the rest of the interface to something darker, as the brightness of the grey background kind of works against you when trying to see dark shades.