The practice tracks are prepared using the Myriad suite of software from www.myriad-online.com. The output is the MP3 files which we use for practice. The Myriad software also produces MYR files. I have started to add the MYR files to the website.
Some singers find using these file which are played using the Melody Player component of the Myriad software is easier for learning the music.
The Melody Player software can be downloaded here for free.
Caution: Using Myriad is not for the inexperienced user, but it is very useful. I will add more information in due course.