Hmm... well, I have found AllMusic.com to be just excellent. Even obscure discs that I've ripped from my collection, that don't have an entry in Gracenote are fully outlined in AllMusic.
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And, it *is* possible to retrieve the AllMusic information programmatically, as this is exactly what Roon uses for their own meta data.
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(Note: I started composing my reply yesterday, but disappeared down the rabbit hole for a while, "researching" the current state of affairs, and while there has been improvement for mainstream releases, I think the classical metadata currently available from diverse sources of unknown provenance is still unfortunately less complete and less accurate than analytically inclined collectors want, and often frustratingly conflicting from one source to another.)
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Thanks, I was hoping you'd reply with something thoughtful, constructive, and offering hope - and you have!

My post was (intentionally) somewhat provocative, and there are some rays of light, such as the Sonata db mentioned previously, and now you've brought another to our attention. I wonder who provides metadata for Qobuz?
It's been a while since I explored AllMusic's database, and your experience, and the fact that the db is available programatically, is very encouraging. I hope that the cost of access to the db is acceptable for Bryston to use it as a metadata provider, or possibly as an optional user-paid enhancement.
When I last spent some time with AllMusic, I encountered many absent or incomplete entries. I'll spend some time to check it out again. A quick peek at the site shows AllMusic is now using TiVo (Rovi) for metadata, the same company that provides metadata for Spotify, iTunes, and others, according to the FAQ. TiVo is large, and pervasive enough, that it may prove to be the winner in the metadata game.
If others are familiar with other high-quality metadata providers that Bryston could pair with, please speak up!
Shifting gears a bit...
I'm not likely to go with Roon at this point, though I understand the appeal of a well-designed and supported UI, which seems to be a large part of its benefit, along with well-curated data and very competent playback. I'll explore it again, as I haven't checked into it in a while, but I remain wary of committing to a closed ecosystem this early. The cost will slow down some potential users, but it may be what's required to gain access to the best quality database available and a well-supported and graceful UI. The need to run Roon Core separately will also be a bit of a disincentive for some. Perhaps, as I believe has been asked in passing, the BDP-3 is suitable to run Roon Core without impacting sonic performance, though as more "stuff" gets added to the BDP, the potential to degrade its audio performance needs to considered.
All this discussion of Roon brings another question to mind... Can (should?) Bryston attempt to make the world's best all-in-one platform for organizing and playing digital music, or should (must?) Bryston focus on its core competencies and provide playback hardware that provides the best possible audio reproduction of digital music, be that on shiny disc, local storage, USB-attached drives (flash/SSD/spinning), stored on a local NAS (consider the different protocols), streamed (again different, often proprietary services or protocols) etc.? The Bryston "endpoint" as the obvious partner for any one of various high-quality providers of "core" music services (music/media servers and software service providers)?
It may be that the goal of a single-box solution that not only handles playback impeccably, but manages large and diverse collections with grace and efficiency, meeting the needs and wishes of all the various enthusiast users is impractical and intrinsically inefficient. Perhaps Bryston needs to provide a competent, but not necessarily class-leading on-board system for managing a "reasonable" collection, and work as hard as possible, both in the engineering realm and the partnerships with providers of synergistic software and services (e.g. streaming providers, media-server vendors, and collection-management software) to enable the music enthusiast to assemble a combination of hardware and software services that is tested, robust, elegant, and tailored to the individual's needs.
Bryston was an early entrant into this category of playback hardware, bringing first-rate audio performance and stability (Bryston hallmarks) to the table. However, the world is much messier now, and users' desires and expectations have exploded beyond playback of files ripped from CDs or downloaded to local storage. People want media servers (not just repositories of music files) with NASs, SANs, cloud backup, streaming of multi-channel audio and video in extreme resolutions, etc. Think of all the various communication protocols that need to be supported, file types, and the impact of video (HDMI & HDCP - shudder!)
Bryston customers want to retain the cherished benefits of owning Bryston - impeccable performance, exceptional reliability, true and long lasting support, but Bryston may not have the resources, or the will, to reform the world. We are still in the wild-west phase of development of digital entertainment for the discerning enthusiast, and Bryston will presumably analyse the market and choose to design and market products that meet the needs of "reasonable" enthusiasts with goals consistent with Bryston's, and that will provide a sensible and sustainable return for the company. That constrains what is possible - Bryston is not Apple, and is not likely to define a new category of music appliance.
Thanks - keep the discussion going!
Syncytial.