Intermediary commit. Nothing's working, everything is broken. Let's start over now...

include/config.h

@@ -1,9 +1,32 @@
 #pragma once
 #include <Arduino.h>
 
-#define PIN_SD_CS            D1
-#define PIN_VS1053_CS        D2
-#define PIN_RC522_CS         D3
+// Pins according to https://www.instructables.com/id/NodeMCU-ESP8266-Details-and-Pinout/
+// D0 = 16
+// D1 = 5
+// D2 = 4
+// D3 = 0
+// D4 = 2
+// D5 = 14
+// D6 = 12
+// D7 = 13
+// D8 = 15
+// A0 = 17
+// Other usable pins:
+// 6, 7, 8, 11 not readable
+// 1, 3, 6, 7, 8, 11 nor writable -> 1 (TX) and 3 (RX) can be used read-only
+// 9 -> S2
+// 10 -> S3
+#define RX 3
+#define TX 1
+
+
+#define PIN_SD_CS            D4
+#define PIN_VS1053_XCS        D8
+#define PIN_VS1053_XRESET    D3
+#define PIN_VS1053_XDCS    D1
+#define PIN_VS1053_DREQ    D2
+#define PIN_RC522_CS         D0
 
 #define PIN_BTN_VOL_UP       D4
 #define PIN_BTN_VOL_DOWN     D5