Are you wanting to put songs in wav or flaac Format or something? I feel like a decently size used iPod wouldn’t be a whole lot more than $100 and 100 GB could hold 10,000 songs in high-quality 320 kB/s or so.

It sounds like you’re trying to build an iPod classic with Bluetooth

I DJ weddings for about 10 years and literally had my entire entire DJ library backed up on one

MVP 🏆

Old iPods are coming into fashion because even younger folks are wanting something like this.

I would consider buying a refurbished iPod classic on eBay. Simple and elegant. User friendly. Do you really need the Bluetooth part?