https://www.musical-u.com/learn/audiation-to-be-a-better-musician-use-your-imagination/
Audiation is to sound what visualisation is to images. It helps you peel away the layers in music.
As musicians, we have to process a lot of information in a very short amount of time. When we hear music, sounds are translated into concise items which then fit contextually into a space of time. Furthermore, if we are performing music, we are also producing even more sounds at the same time!
Zoltán Kodály created his revolutionary teaching approach based on using “inner hearing”, allowing his students to develop their listening, aural and performance skills in singing and ensembles. It trains people to be able to internalise and hear music inside their heads, without listening to or playing anything in the real world.