In the past, to see & hear Dolmetsch Recorder Method pieces, Music Theory Online examples or e-Music scores, you needed to install the Scorch plugin from Sibelius Software.
It was free, incorporated no spyware, took less than a megabyte of disk space and you needed only install it once.
Unfortunately, Scorch used code that browsers considered 'unsafe' and slowly support for it fell away.
The good news is that Avid, Scorch's owners, are about to introduce a new service to play web-embedded Sibelius scores.
There is more information here: Sibelius Cloud Sharing Coming Soon.
Once the service is up-and-running we will rebuild our webpages to make use of it, and to replace the inactive Scorch-enabled material.
This will take a little time so please be patient.
Our plan is to convert the Music Theory first and each updated page will be marked as 'updated to Sibelius Cloud Sharing' once each chapter has been fully converted and thoroughly tested.