Hey, thanks!
There's some contact info on my website (https://www.mattjhart.co.uk/), I'm interested to see what you've recorded if you send me message by email or Discord!
As for how I made it, it was entirely made in Deflemask, which is what I use for chiptune stuff nowadays (I use it mostly because it lets you use Mega Drive sounds). So I just inputted all the notes in that and it lets you export it as a .gb ROM file. I'm not aware if there's currently a way to export music from Deflemask in a way that can be used in GBstudio to allow me to make a more customised ROM, hence why my ROM is visually very simple!