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Q. How best can I clean up old cassette tape recordings?

I have several cassette tapes of concerts and recitals recorded when I was at music college in the '70s, which I want to transfer to CD, cleaning up the recordings in the process. The tapes are in good condition, the only sign of ageing being the odd loose pressure pad, which can easily be fixed. The recordings were made on good‑quality stereo cassette decks, some with and some without Dolby, some standard ferric tapes and some chrome‑dioxide. The main problem is that in a lot of the recordings the mics were quite a long way from the performers, so on playback the levels need to be high, making tape hiss quite prominent.

I realise these recordings are never going to be perfect, but I'd like to clean them up to the best standard I can. My recording setup is based on a Mac running Cubase 7, but I'd be willing to invest in any other software which might be more dedicated to this job. I'd appreciate any advice or tips you can give me regarding settings, any available plug‑ins or even specialist applications. Mark Dawson, via email.

Sound Soap remains an easy-to-use and accessible tool for basic noise-reduction tasks, but there's a huge range of alternatives with more sophisticated processes on offer.

SOS Editor In Chief Paul White replies: Probably the most effective type of software for your needs is what is generally termed multi‑band noise removal or reduction. Most of these products work by learning the spectrum and level of the hiss from a supposedly silent section of the tape, for example between tracks. This information then sets the thresholds in what is essentially a multi‑band expander, so that whenever the signal falls below the threshold level in each band (which, after learning the noise sample, is set automatically just above the noise floor), that band is reduced in level. The more noise reduction you apply, the more likely it is that 'chirpy' side‑effects will be heard, so setting is always a compromise between retaining sonic purity and reducing the background hiss, with the more expensive systems generally producing better results. Suitable solutions range from the free WavePad software (Mac and Windows) to more serious tools such as those offered by companies such as Waves, Sonnox and iZotope. Companies such as CEDAR and Sonic Solutions produce the very best in noise-reduction solutions but these tend to be (very) professionally priced.

I used find that BIAS's Sound Soap software offered an affordable and easy‑to‑use approach, and while BIAS may be no more, you can still get hold of Sound Soap for Mac from Soundness (www.soundness‑, and a Windows version is planned. If you do a Web search for any of these packages, you will inevitably come across similar products, and again, some of the lower cost or free ones may be suitable for your needs: WavePad is certainly a good place to start. Using any of these systems effectively requires a little patience, but it doesn't take long to get a handle on what they are capable of and how best to apply them.