It’s a reasonable course for helping yiu identify a single line of notes across the two staves. Or maybe just the “right hand” upper/trebble clef stave (the bormal one for most instruments).

It does teach a little anout scales. It wont teach chords. It doesn’t go very far into time signatures. It only has you play a virtual keyboard so it’s useless for learning how to feel your instrument.

It’s quite fun. My kid plays it every day and it’s helped get them feeling more confident to sit at our piano and noodle around. As a noodler myself, this seems valid.

It wont get you good enough to play pieces with other musicians, or to compose with weatern harmony. You’ll need extea tutorials for those.

Duolingo is garbage based on dry cramming.

For music it is pretty useless