How do you ask someone out that you’ve known for a long time?

I’ve (20M) recently developped a crush for a girl (19F) from my old highschool class (we’ve both graduated this summer). While my crushing has been quite the uncomfortable emotional rollercoaster in and of itself, that’d be another post altogether.

Anyway, we’ve never really been especially close throughout highschool but in the past weeks, we’ve gained some trust and appreciation for one another. Whenever we talk, we do so very openly and personally. I think part of that is that we’ve known each other for so long that it’s quite easy to lower our barriers. Which is great because I really enjoy talking to her but also concerning because it feels eerily close to being friendzoned (former classmate-zoned?).

In a very out-of-character display of something resembling charm, I’ve invited her to my place so that I could show her the basics of the bass guitar (something she’s shown some interest over the years) and she happily agreed. In my head, this pretty much feels like a date, I highly doubt that it’s the same for her (and I’m quite aware that she would be right). I’d hate making her feel uncomfortable but I’d also like to show my interest in her somehow.

Most of the times we’ve met since our graduation, it has been with groups of other people or under some pretense. It’s never been “I’d like to meet with you because I’d like to spend time with you.” In some sense, my doubts and fears have nothing to do with us having known each other for four years now, but I’m concerned that she’s unable to see anyone but a classmate in me. That for all appreciation she might show, it’s doomed to be platonic because that’s what she’s known me as for most of our time together.

Any advice on how to deal with this situation would be greatly appreciated!