Add 2 more variables for AudioFeaturesObject

[CB00]

Hi, I'd like to request two audio waveform variables be added in the API return for AudioFeaturesObject:

1) primary & secondary frequencies (e.g. using a Fast Fourier Transform or Discrete Cosine Transform)

2) amplitude of these 2 frequencies in relation to a blended average of others, or on absolute scale.

This would be very helpful for audio visualization/animation. Thanks to the devs, goes without saying that this is a great API already!