YouTube Music isn't perfect, but it's still heaven for music nerds

The new, ad-free YouTube Red subscription service that just arrived is only one part of Google's big re-imagining of YouTube taking place this year. The odd-duck YouTube Music Key service has graduated from beta and is being re-introduced as YouTube Music. The new app is available today for Android and iOS users, and you can use it whether or not you're signed up for YouTube Red.

At first glance, YouTube Music is a bit of an enigma -- after all, Google already offers its own take on music streaming with Google Play Music. But after spending some time with the new YouTube Music app, it's clear that the new service isn't meant to mimic Google Play Music, Spotify, Apple Music, and all the rest. Instead, it's a music service for the millions of people who already do most of their music listening straight through YouTube itself. And if you're the kind of listener who likes to go deep down a band's rabbit hole, the wild depth of unofficial music on YouTube makes this app a lot of fun.

As with most music apps these days, YouTube Music provides a fast way to just start playing songs you might be interested in. From the app's home screen, the personalized "my station" option will automatically start playing back a selection of music based on both your music playing history on YouTube as well as any music content you've "liked." That's one of the potentially great things about YouTube Music -- many users will have a huge history for the app to pull from, which will help it recommend you better songs right off the bat.

As you scroll down, you'll see the standard genre-based stations (indie, alternative, hip-hop and so forth); again, they're all created based on your YouTube history. Playing any particular song that's recommended to you will also start a station based on the artist, as you might expect -- it'll all part of YouTube Music's focus on keeping music playing continuously once you kick things off.

This app is designed for you to go deep down the long tail of YouTube.

Any station you're listening to is customizable, depending on how adventurous you're feeling on a given day. There's a three-stage slider you can adjust; on the left, you'll get mostly more music from the artist you're listening to (or, if you're listening to a genre station, songs that are more closely related to things in your listening history). As you move the slider to the right, you'll get more adventurous choices that might be outside your listening wheelhouse. There are persistent "thumbs up / thumbs down" buttons for rating what you hear, and YouTube Music helpfully collects anything that you like in its own tab so you can easily return to it later.

If all of this sounds like table stakes for a music service, that's because it is -- but given this is YouTube, there's an obvious focus on video. Officially released songs will play alongside their officially released videos, and YouTube Red subscribers will be able to switch back and forth between video and an audio-only mode that you can play in the background while doing other things with your phone. The audio-only background mode is smart enough to know to present you with an audio-specific file; you won't suck up unnecessary bandwidth streaming a video you're not watching. And if you're watching a song with a more elaborate, theatrical video -- think Michael Jackson's "Thriller" -- audio-only mode pulls a version of the song more appropriate to listening on headphones. You won't hear the cinematic, 13-minute version when you switch to audio-only, but rather the song as it is on the album.

Beyond music videos, the biggest differentiator for YouTube Music is the vast amount of content on the site that isn't a standard music video for an official release. If you're listening to a song or watching, you can check out an "explore" section to find related content. Think live performances, covers (from artists big and small), remixes, demos, and so forth -- the YouTube team has spent the last year organizing all of its music content and identifying appropriate links between videos so you can dig deep into a particular song or artist and find the wide variety of content on YouTube that relates to it.

It's the kind of feature that only YouTube can offer, and it's probably the most compelling part of the service. I love seeing how bands evolve songs when playing them live over time, and I imagine the YouTube Music app will make feeding this obsession a lot easier than it used to be. Yes, all this content is available in YouTube proper, but YouTube Music makes it easier to find these connections and do that on mobile.

If you need robust offline saving features, you'll need to look elsewhere.

YouTube Red subscribers get a few other benefits when using the YouTube Music app, as well. Besides audio-only playback, everything is ad-free (naturally). And there's a smart feature called the Offline Mix Tape: it's a playlist that auto-updates every day and saves to your phone's storage. You can decide how much space it uses and whether you want it to be audio only or include videos, but once you've done that YouTube's algorithms take over. The selection of music will automatically change and sync to your phone daily so that you always have fresh songs for when you don't have an internet connection; the songs themselves are chosen by your listening activity and what you've liked.

It's a clever feature, but unfortunately it's the only offline option in YouTube Music. There's no way to otherwise save videos for offline playback in the YouTube Music app -- for that, Red subscribers will have to use the standard YouTube app. When searching in the app, you'll have access to essentially the same catalog as in Google Play Music, with the option to play back an audio-only album -- but you can't save that music for offline listening. If you're more inclined to save a bunch of albums for your subway or plane rides, you'll need to use a second music app.

That's probably the biggest problem with the YouTube Music. There's a lot of interesting ideas coming to fruition here for people who use YouTube as their main music player, but there are also a lot of features missing in a world where many are stuck with limited data plans. The lack of a true library, playlist creation and more robust offline features means that a large subset of consumers won't be able to use YouTube Music full-time.

However, when you sign up for YouTube Red, you also get a full subscription to the more traditional Google Play Music service. Coupling that with the on-demand long tail of content available on YouTube makes for a pretty all-encompassing musical experience. If you're the type of listener who prefers full albums and making your own playlists, YouTube Music can be a nice compliment to Google Play Music -- but if you're someone who lives their whole musical life on YouTube, this new app will provide a strong way to take that experience on the go.