Only one out of three modes in Rings uses modal synthesis (green). The other two modes (orange and red) are Karplus Strong with a few twists (2 pole IIR absorption filter with phase compensation instead of the usual FIR; a non-linearity emulating the curved bridge of the tanpura; AP dispersion filters…).
String instruments, especially when the play low notes, can have very rich spectra with many harmonics - with a 100 Hz f0, the 100th harmonic is still well within the audible range! If you want to simulate that with modal synthesis, you need that many filters in your filter bank, and that would be too much for our little Cortex M4. Try playing a low note (say a f0 at 80 Hz) with Rings in modal mode, with STRUCTURE at Because Rings is limited to 60 or so bandpass filters, there’s nothing in the spectrum above 6400 Hz, and the resulting sound is dull, almost cellphone/youtube like.
If you look back at the product history… Rings has a modal synthesis mode because it was supposed to be, initially, a standalone version of Element’s resonator section (with no other mode).
Elements uses modal synthesis because this is what offers the largest palette of “physically inspired” sounds in a same continuous space, without the need for mode selection buttons.