When the project was originally proposed, 6 viewers were implemented using MPLH5 and it had been decided that they were old and needed some improvement. D3.js was a suitable javascript library, and it turned out to be a good tool for doing this task.
The original proposal aimed to update two or three visualizers, more specifically the Wavelet Spectrogram Visualiser, the Fourier Spectrum Visualiser and if the time allows until the end of the project, also the Complex Coherence Visualiser.