Hi, many thanks for the reply.
Run fpcalc over the song to generate a fingerprint (a long string of ascii characters)
This is then posted to the web service in parameters to the url.
you then get a response back in json where you can find the id's.
Done all this, sorry, I should have made that clearer.
According to the docs found here, it says:
Even though compressing HTTP requests is not a common practice,
our web server supports GZip-compressed bodies for HTTP POST requests.
If you compress the body using GZip and set the "Content-Encoding" HTTP
header to "gzip", we will decode it before parsing the parameters.
Because there is mention of compressing the request due to the size of the fingerprint, I thought this would have been the preferred method. Again, apologies if I have misunderstood.