Hi Erin,
Honestly both databases will do the job just fine. I personally prefer Postgres.
Much more important is how you store the audio. While you could technically use a blob type column, it's really not ideal to be storing audio files which are "several hours long" in a database row. Instead consider storing the audio files in an object store (hosted options include backblaze b2 or aws s3) and persisting the key (which references that object) in your database column.
Clojure is a Lisp dialect, so if you like Lisp that's probably the way to go. Scala is more popular and broadly used, and has a larger job market especially for data engineering. Both are functional but Scala is more interoperable with Java libraries, probably a big factor in its popularity. I prefer Scala for a number of reasons, but in terms of jobs Scala is the clear leader.
I would disagree that Scala is more interoperable with java libraries altho it depends. I agree implementing abstract classes if required might be more tricky but simply calling Java is simple.
I've not used Scala.js but JavaScript interop is simple in Clojure and React.js is particularly well supported.
Scala.js interop with JS is amazing too, and there are numerous projects to integrate seamlessly with the React world. For instance: https://slinky.dev/
