Web APIs for audio are under active development. The W3C has formed a working group where use cases and two specifications (Web Audio API and MediaStream Processing API) are being developed. Chrome and Safari are shipping experimental versions of the Web Audio API now, and Firefox will soon be shipping experimental versions of the MediaStream Processing API (it's available now in a special build). Firefox 4 onwards also includes the simpler Audio Data API. I believe all of these APIs provide sufficient functionality to build the audio portions of media playback with working audio-visual synchronization.
Open about:memory and see where the memory is going. And if you think the use is excessive, please file a bug including the about:memory data and any details you know that would aid in reproducing the problem.
Averaging the results? They probably discard outliers too. Unusually high output is something you'd want to be aware of rather than hiding it in an averaged result.
The linked article seems to refer to an incorrect star. The correct one (which is also named in the BBC article linked from this article) is BPM 37093: http://en.wikipedia.org/wiki/BPM_37093