My suggestions are intended expand upon the .NOTE format by adding additional filtering options inside the instrument effects section.
- Add a second filter.
Instead of being limited to a single filter, you can now set two filters. For example, you could set both a low pass and high pass filter, this would give you more control over the cutoff points making it better than just a single band pass filter. Another example, you can combine two of the same filters for a steeper slope, such as setting two high pass filters to clean up a particularly muddy instrument.
- Add a three-band parametric equalizer.
The three band EQ will consist of a low shelf, peak, and high shelf filters. No visualization is necessary, just three frequencies controls, three gain controls, and a width value for the peak filter. The shelving filters would be great for subtly boosting or reducing a wide band of frequencies and the peaking filter for homing in on a specific frequency. The EQ would be quite useful as you can now boost frequencies such as adding extra presence in the high end, adding extra girth in the low end, or you can reduce frequencies to clean up an instrument without completely cutting the frequencies out like the pass filters do.
The additions of a second filter and a three-band parametric equalizer would be a great upgrade to the .NOTE format. Many users would get great value out of these tools as these would give them much greater control over shaping the tone of their instruments, allowing them to make much better sounding music.