https://www.hooktheory.com/ https://www.hooktheory.com/ This is a very good place to start and at least validate that you have the foundations. I mean both the

https://www.hooktheory.com/ https://www.hooktheory.com/ This is a very good place to start and at least validate that you have the foundations. I mean both their courses and chord progression/melody database. Also, playing around with their composer is a very very easy and pleasant way to actually grok harmony. Rhythm/dynamics/etc you would need to learn somewhere else, but most people don't have a problem with that anyway. Disclaimer: While hooktheory is a better resource than the ones posted by others, I see that they have started marketing their product as 'Pro'. This cannot be further from the truth - there is nothing 'Pro' about it - it is pure schoolboy stuff, it is just very well done.