I believe there's about 86 songs or something around that are broken up into individual tracks. For example, Weezer's King of the World has a guitar, bass, drums, and vocal card. In in a cool way. it means hating/liking music isn't as important since you are really using basic parts that can be altered pretty extensively to make new music. The other three card types are effects, which are subtle enough to not be obnoxious but can also be overwhelmed by other tracks. Then there are cards with all tracks on them meaning it has vocals, instruments, etc. on one card and you choose which track is played by where you place it. These are powerful, tend to be popular songs that are often classics and are much fewer in count (around 30 of the total cards). Lastly, there are "baffler" cards that are just fun but odd pieces for novelty (e.g. Doctor Who Theme, beatboxing, etc.). Harmonix officially announced a new season with at PAX and showed a new mechanic but no songs or full details have been releases.
As I mentioned above it's more about your interest in basic but very streamlined music mixing application by way of cards. The game itself is more the magical feeling of hearing a song evolve dynamically as you play a basic but entertaining card game.
I have to use a bluetooth speaker or I won't bother. Bluetooth headphones are probably even better if you prefer. Totally agree that thing should be an Xbox or PS4 app that pairs with board. It's a real lost opportunity. Also Amazon sells every set complete often at a 15% discount so it's pretty easy to complete the collection if you really want but 50% deals I've seen occasionally at retail much less choice.
Edit: Amazon pack sets are now ridiculously priced. They were 25 bucks for 6 which is decent for a guaranteed complete series but are now double.