Sorry for the delayed reponse, here is a demo page: my song
is the music NFT playable on the claim page directly?
Yes, you can play it on the page.
are there formats / size limits?
Nothing you would reasonably hit imo.
can we select several versions of a cover image for the same music NFT (ex: have a golden cover image , a regular color image for rarity)
Only one cover image, if you want different ones you will need to create multiple claims for each cover image.
will those ERC721 tokens be also reflected on Foundation?
Yep, they should be.
Are there other specific features (planned) for music like playlists etc?
Nothing at this moment.
Regarding the price of such drops, I see that you set it for free, are there other options besides free / fixed price like Free pricing? (users would decide on how much they would pay)
Yes indeed something quite flexible for some of the music releases we are planning, so that they can mint for 0 ETH (+ gas fees) or indeed give the amount they can as you mention.
Also, are you using your music pages releases only through Manifold or your mint page can be integrated on another website?
Doesn’t have to be through the Manifold website! We provide a set of widgets that can be used to build custom sites by any developer using Manifold as the backend. Widgets - Manifold Docs