I have a very large number of old cassettes, many of them recordings of live shows from the radio, and therefore irreplaceable. The make of all is TDK, which I always found to be reliable. I am in the process of transferring them to CD, but some - and one in particular that I love and do not want to lose - have gone 'wobbly' in sound (sorry, best way I can describe it). It starts well, but about 10 minutes in the sound trembles.

I thought rehousing the tape in a new cassette casing would help - it didn't.

Before posting I looked up previous threads on cassettes and did not find the answer. Your wisdom and experience will be hugely appreciated.

Yours in hope,
Ian