In my recent expeditions to the darkest corners of my garage, I've found a load (there's a pun in there somewhere) of old audio tapes containing Sinclair Spectrum code. These aren't commercial titles, they're record-your-own-code blank tapes from the early 80's: I'm certain they contain magazine type-ins and terrible games and graphics, authored by my 11-year-old self.
The tapes are mostly physically intact, having been kept in their own container (see the photo). However, listening to the audio (with the practised ear of someone who grew up listening to Spectrum games load), it's noticeably muffled, and there's a bit of "wow and flutter" - wobbly pilot tones and the audio coming and going. I wasn't expecting miracles after 30-odd years, but I'm still hopeful that there's going to be some way to at least partially recover some of this data.
I've hooked up a tape deck to a Windows laptop and captured the audio into Audacity. I've wound the tapes end-to-end a couple of times (both to free up any stickiness and to hopefully counteract any print through). Regardless, MakeTZX and audio2tape fail to pick up anything useful in the files. I know there's a few Spectrum emulators that can play back WAVs; Spectaculator shows signs of picking up the pilot tone in some of the files, but the audio seems to be just too degraded to load anything.
Is there any post-processing I can do on the audio to clean it up enough to hopefully allow an emulator, or MakeTZX/audio2tape to extract the data? Does anyone have any other advice for enhancing the audio to least be able to identify what each block of code is? Are there any conversion utilities or emulators (for any platform) that are more forgiving of audio quality, or designed to help rescue degraded data?