I have a music blog and I hope to have a wonderful audience. I want to offer options like being able to post and read small musical ads or/and discuss music subjects like modes etc… Is it easy to add discourse on your website? Like have a page forum: https://soundsirius.digitalpress.blog/forum
you do it using Discourse for sure. Now, discourse is a separate service so you will have to pay for it (hosting) or host it by yourself.
If this will add value to you, it should not be a problem.
Pretty much what @gregpozo said, and I would probably put it on a subdomain too. Have you seen our Discourse integration guide? Could be useful for sparking new topics from new blog posts: