add necrodancer_shop.sh in case you want that

scripts/necrodancer_shop.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p bash ffmpeg
+#shellcheck shell=bash
+set -euo pipefail
+
+if [[ $# -ne 2 ]]; then
+	echo "usage: $0 /path/to/necrodancer /path/to/output"
+	exit 1
+fi
+
+# Original songs named zone<zone>_<level>.ogg
+# Remixes named zone<zone>_<level>_<remix>.ogg
+# I think remix IDs are:
+# (none): Danny Baranowsky
+# 1: A_Rival
+# 2: Jules Conroy
+# 3: virt
+# 4: Girlfriend Records
+# 5: OverClocked
+# 6: Masafumi Takada
+# chp: Chipzel
+
+music="$1/data/music"
+sounds="$1/data/sounds_streaming"
+
+for zone in {1..4}; do
+	if [[ $zone -eq 3 ]]; then
+		suffixes=( "c" "h" )
+	else
+		suffixes=( "" )
+	fi
+	for level in {1..3}; do
+		for remix in "" _1 _2 _3 _4 _6 _chp; do
+			for suffix in "${suffixes[@]}"; do
+				ffmpeg -y \
+					-i "$music/zone${zone}_${level}${remix}${suffix}.ogg" \
+					-i "$sounds/zone${zone}_${level}${suffix}_shopkeeper.ogg" \
+					-filter_complex amix=inputs=2:duration=longest \
+					-b:a 128k \
+					"$2/zone${zone}_${level}${remix}${suffix}_complete.opus"
+			done
+		done
+	done
+done