It's a Google Pixel 2 XL from back in 2017 that I had laying around as a backup phone. The app is Poweramp that I purchased at a steal for $0.99 way back when it was only $3.99 for the full version. Currently it's priced at $6.99, but I feel that it's worth it. You can also wait for it to go on its periodic sale, last time it went on sale during Thanksgiving I believe for $2.49 if you want to save a quick buck.

There's also a skin applied that I got for free years ago called Aurora now priced at $1.49. It gives Poweramp a cleaner look compared to default.

Additionally I use the Wavelet app for it's AutoEQ feature.