https://www.musical-u.com/learn/how-can-i-play-the-music-i-hear-in-my-head/
Learning to play what you hear in your head is a great benefit of musical ear training.
Before doing ear training, many musicians feel like they can imagine amazing music – but then can not bring it out on their instrument. To play the music you imagine on your instrument requires a combination of listening skills and instrument skills.
There are three steps to follow if you want to be able to do this: https://www.musical-u.com/learn/how-can-i-play-the-music-i-hear-in-my-head/