I will make an unadulterated recording this weekend of several of my Hohner melodicas, including the cassotto.
I am slowly formulating a timbre scale in my mind that looks like this:
1. Super bright, brass-like, harmonically rich = Suzuki Pro 37v2
2. Full, rich, somewhat bright sound = Yamaha P 25/32/37D series
3. Full, rich, slightly darker sound = Hohner Piano 36
4. Darker, softer, smoother sound = Hohner Piano 26/27/32 series
5. Very smooth, hollow sound, least amount of harmonics = Hohner Cassotto 26/27 series
The difference between 2 and 3 is pretty subtle.