Internet has a great global project named Wikipedia which is an encyclopedia done through the contributions of the Web surfers. This means that, if you feel prepared for the job, you can writte an article on wagnerian harmony and upload it to Wikipedia, of course following certain rules and passing some filters. Each language has its own Wikipedia which will be more or less large depending on the number of received contributions.

Here you will find the versions of Wikipedia corresponding to the different, most common european languages, specially because the local subjects are likely to be treated in a more precise and extensive manner on the Wikipedia of the region.

We start with the English version which, with more than 2,800,000 entries, it is probably the most extensive.  

Wikipedia in Catalan, with near 170,000 entries.  

Wikipedia in Spanish, with more than 450,000 entries.  

Wikipedia in German.  

Wikipedia in French.  

Wikipedia in Italian.