This repository holds the source code and schematics for the video https://www.youtube.com/watch?v=srmNbi9yQNU
Final schematic:
Arduino source code for the first test:
Arduino source code for the second test:
There is also an improved Arduino source code for the second test, where a buffer is used to store the bytes retrieved from the SD Card file and an interrupt on the Arduino's Timer 2 is used to improve timing when playing a song:
Python script to convert YM files to a custom file format SNG for the AY-3-8910: