Reddit mentions of Numerical Methods that Work (Spectrum)

for audio and sensor data:

for FFT stuff you probably have already read Brigham, if not do read it.

Acton has good books
https://www.amazon.com/Numerical-Methods-that-Work-Spectrum/dp/0883854503
and
https://www.amazon.com/Real-Computing-Made-Forman-Acton/dp/0691036632?ie=UTF8&ref_=asap_bc

for time-frequency look into the S-transform. It's like wavelets but it has the local phase spectrum that is consistent with the discrete fourier transform. There is also an orthonormal version of the S-transform.