{
  description = "A tool for organising a music library";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    utils.url = "github:numtide/flake-utils";
    flake-compat = {
      url = "github:edolstra/flake-compat";
      flake = false;
    };
  };

  outputs = { self, nixpkgs, utils, ... }:
    {
      overlay = final: prev:
        let
          system = final.system;
          fold-to-ascii = final.python3Packages.callPackage ./nix-extra-deps/fold-to-ascii.nix { };
        in {
          fold-to-ascii = {fold-to-ascii = fold-to-ascii;};
          musicutil = {
            musicutil = final.python3Packages.buildPythonApplication rec {
              pname = "musicutil";
              version = "latest";

              src = ./.;

              postPatch = ''
                substituteInPlace musicutil/meta.py --replace 'ffmpeg_path = "ffmpeg"' 'ffmpeg_path = "${final.ffmpeg}/bin/ffmpeg"'
                substituteInPlace musicutil/meta.py --replace 'ffprobe_path = "ffprobe"' 'ffprobe_path = "${final.ffmpeg}/bin/ffprobe"'
                substituteInPlace musicutil/meta.py --replace 'r128gain_path = "r128gain"' 'r128gain_path = "${final.r128gain}/bin/r128gain"'
              '';

              doCheck = false;

              propagatedBuildInputs = with final.python3Packages; [
                mutagen
                fold-to-ascii
                pyyaml
              ];
            };
          };
        };
    } // utils.lib.eachSystem (utils.lib.defaultSystems) (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          overlays = [ self.overlay ];
        };
      in {
        defaultPackage = self.packages."${system}".musicutil;
        packages.musicutil = pkgs.musicutil.musicutil;

        defaultApp = self.apps."${system}".musicutil;
        apps.musicutil = {
          type = "app";
          program = "${self.defaultPackage."${system}"}/bin/musicutil";
        };

        devShell = pkgs.mkShell {
          inputsFrom = [ self.packages.${system}.musicutil ];
          buildInputs = with pkgs;
            [
              nixUnstable
              mutagen
              self.packages.${system}.fold-to-ascii
              pyyaml
            ];
        };
        lib = pkgs.musicutil.lib;
      });
}