Please take a look at the README.md of SoundCheck repository before using the website.
Alternatively you can also copy content from some of the files with .raag extension from this folder, paste on the editor, click the Run button at the top right of the editor to see the performance on Output tab of the right window, by clicking on the pause button of the player, once the right window is populated with the required response. But I will still request you to go for the first option.
The styling of the audio player, that is there in the Output tab of the right window has been copied from this repository. The contributor presents a walkthrough of the code in this youtube video, feel free to take a look.