Music: six more dungeon pieces and six surface pieces with flute, harp, birdsong and wind

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -202,7 +202,9 @@ On phones: tap to use a tool, drag to mark or move, two fingers to zoom and turn
 - **Rust**, compiled to **WebAssembly**, with [macroquad](https://github.com/not-fl3/macroquad) - one small module, no engine, no plugins.
 - A real 3D isometric world in pixel art: chunked meshes, flickering point lights, a glow pass, particles,
   billboard sprites with eight viewing directions, every frame of it drawn by code - **no image files** except the font.
-- Procedural chiptune soundtrack as FastTracker 2 modules with its own XM replayer and synthesised sound effects.
+- Procedural chiptune soundtrack as FastTracker 2 modules with its own XM replayer and synthesised sound effects:
+  47 pieces around one leitmotif - in the dungeon dark and minor, above ground bright, with flute, harp, birdsong
+  and wind; the music follows the camera between the two worlds.
 - A tiny Rust savegame server (axum, Argon2 passwords) - optional; without it the game uses savegame files.
 - 18 languages: German, English, Spanish, Portuguese, Dutch, Danish, Norwegian, Swedish, Finnish,
   Russian, Croatian, Hungarian, Serbian, Romanian, Slovak, Czech, Italian and Greek – chosen from a