It’s a tune by the German Eurodance group Snap!, that was played a lot one summer as I travelled across Europe. I hear just one refrain from it – “It's a soul companion/ You can feel it everywhere” – and the late nights and sandy beaches come immediately to mind. But were I deliberately to try and remember something particular from that holiday, without the music, I would recall nothing as immediate or emotional. This is an experience shared by everyone: hear a piece of music from decades later and you are transported back to that particular moment, like stepping into a time machine. You can feel everything as if you were actually there. The relationship between music and memory is powerful, and new research is hoping to discover how these memories work for therapeutic effect. It is already used to help dementia patients, the elderly, and for those suffering from depression.

https://www.bbc.com/culture/article/20140417-why-does-music-evoke-memories