Thanks for your question and for the link to your beautiful site; very helpful.
It looks like you have already created posts or pages for each of your compositions and have grouped them into categories such as “ponteradio”, “pensieri” and “libera”; is that right?
You have a basic choice to make regarding your site design: 1) you can assign tags, categories and custom field values to the posts/pages for your compositions or 2) you can assign tags, categories and custom field values to the Media Library items, i.e. the MP3 and PDF items.
If you choose to organize your posts/pages you can use WordPress and your theme to do the work; you don’t need much from MLA. You have quite a bit of text material for each composition so this might be a good choice.
If you choose to organize your Media Library items you can use MLA to filter your collection by tags, etc. but you will have to find a way to organize and display the text content as well. Can you, for example, put all the text you want in the Description field for each item?
Either way you must decide how to assign the musicians, genre, year, description, album, etc. values to each composition. Have you worked out how to use taxonomies and custom fields for this? You must also decide how to match the score to the audio file for each composition, and decide if you want more than one audio file and/or score for each composition.
You might be interested in this earlier topic along similar lines:
Alphabetical pagination
I would be happy to learn more about your application and see if MLA can be of help. It will be much easier to continue the dialog by email rather than updating this topic. You can contact me at my web site with any additional information you can provide.
I am marking this topic resolved, but I look forward to hearing from you. Thank you for your interest in the plugin.