[LAU] Re: How to analyse and "optimise" a frequency spectrum? (digitising tapes)

Hey hey,

I have digitised a few last tapes. The sound isn't too bad, but all tapes appear to be a little too bass heavy. Since I only work in the terminal I approach the issue with Csound that provides a lot of tools. All kinds of filters, rms/peak metres, an lufs metre and more. First: did I miss an obvious commandline tool that would produce a reasonable solution for that? There are two main issues that I try to improve halfway automatically. 1. Sometimes the stereo balance is a little wrong with one channel being slightly louder than the other. 2. Imrpoving the frequency spectrum, flattening it a little bit. For 1. I have started by taking the file's peak of both channels seperately and simply multiplying them so the peaks match. Over a whole tape side this should be approximately the same. Or should I go with a different measurement? lufs integrated loudness, momentary or short term maximums? For the second issue, I am unsure. I have split the audio into frequency bands using octaves, more or less. So the first band goes up to 100Hz, the next to 200, then 400, 800 and so on. I have used Csound's tone and atone filters: atone highpass filter: https://csound.com/manual/atone.html and the matching tone lowpass filter: https://csound.com/manual/tone.html Then on each band for each channel I run the lufs metre, storing the maximum momentary and short term values and the integrated loudness. Though I wonder: are the frequency ranges and type of filter reasonable? If so how would I approximate a reasonably flat spectrum? Which values to compare to what? I mean: what kind of measurement to use and should I compare adjecent bands and extrapolate fitting values from that or compare one frequency band's measurement to the same measurement on the unprocessed full-band audio? Any hints and practical suggestions are very welcome. Thank you and best wishes, jeanette