more important: can I upload tracks to Spotify?
Worth checking out this thread…
Also, there are many articles online reviewing and comparing options/services…
I find a helpful article, which covers the ways to add local files to Spotify, you can visit it to see it can work well for you here: How to Add Local Files to Spotify
Besides, Spotify allows free users to do this. No need to upgrade to Spotify Premium, you can upload tracks to Spotify.
To be clear, that isn’t really uploading files to Spotify.
It’s a way to use Spotify as a music player app for your local files, including making them available on your mobile devices.
Only you will be able to play those local files.
Amuse.io has always been a good option, they’ve changed a few things as of late but it still works nicely