Hi Jim,
I used Wave Corrector - http://www.wavecor.co.uk/ - to do my cassette collection. But I don't think there is a Mac version.
I have given up on finding software that will reliably detect BPM. I use http://www.all8.com/tools/bpm.htm and tap for as long as I want at different points in the tune.
Happy dancing,
JohnJohn Sweeney, Dancer, England john@modernjive.com 01233 625 362 http://www.contrafusion.co.uk for Dancing in Kent