At the request of a psychologist friend I am working on theta and alpha binaural beat synthesis for encouraging relaxation and (possibly - depends on the research you believe) hypnotic susceptibility. Basically I want to move the left and right channels of a stereo system respectively up and down a few (2-6) Hz, possibly with time varying control of the shift.
As I retired Analog employee I have an ADAU1701 Evaluation Board and Sigma Studio which has enough power to do the job. I originally designed a simple system with the pitch transposer but it did not work well at all, being noisy, and jumping in frequency.
It is not difficult to build a system from scratch, but it would be much easier if I had access to the Hilbert transform and quadrature VCO functions, which are said to be being released for the ADAU1701 in early spring 2013. (Or, of course, if I could get my thieving hands on a more advanced evaluation board which already has the functions.) I am working to a deadline and will design and debug the complex system if I must, but if there is some way of obtaining these functions for the ADAU1701 in the next few weeks, either because they are ready for release, or as beta versions, I should be pleased to know of it.