Nostria simply get's everything, all the music events and locally caches it, so you can search and discover. That won't scale to massive levels though, that will require an indexer and using the search NIP on Nostr protocol to search on a large scale. Though Nostr is not about global indexing content, it's decentralized and subjective/personalized views, which is why Nostria can filter based upon your following, or follow sets (people), and curated lists. What can also be done, is search the RSS feeds and then produce custom Nostr events so the mapping between Nostr and RSS become more Nostr-native. Using the "q" or something tag as a external link reference.