STFT[frame, freqbin] be the short-time Fourier transform of some audio data.
frame is the index in time, and
freqbin is the index in frequency).
STFT[k, f0] will be close to
... then it could be interesting to store, for each frequency bin
f0, only the differences :
STFT[0, f0], STFT[1, f0] - STFT[0, f0], STFT[2, f0] - STFT[1, f0], STFT[3, f0] - STFT[2, f0], etc.
(such processing is known as delta encoding) ; these differences will be small on average, and this could lead to a reduction of the average bit usage for storage of the audio data.
Can this idea be turned into an efficient audio data compression ?
(I don't speak here about psychoacoustic effects that could lead to use different levels of quantizations for each frequency / or frequency masking ; I know that such ideas are used in MP3 compression).
Edit: as mentionned by @pichenettes, the graph above showing continuity between adjacent frames is the "magnitude plot". The "phase / angle plot" is a bit less continuous :