[rwmj]

The bit rate of a speccy tape recording was only about 1500 bps, and we routinely recorded on the cheapest tapes, and tape machines that were little better. I'm sure it'll be fine.

Technical details for those interested: https://sinclair.wiki.zxnet.co.uk/wiki/Spectrum_tape_interfa...

[anthk]

Minimodem at 300BPS with the audio encoded to OPUS at 64 KBPS makes pretty reliable dumps with a relative small space per hour (~30MB).