Got the score 22250.
For the first time, I played Defender on the original hardware. Ruben & Bobbie in Copenhagen has a machine, and I struggled with the button layout and got this one decent score after spending a lot of 5 DKK coins...
Got the score 26925 in MAME.
Theres been quite a bit of Defender going on on the PD MAME machine. Me and Jeppe are narrowly competing for the top.
Preparing for my talk at Spilbar on 80s game music and audio technology, I looked into the audio implementation of Defender. It's basically a MC6800 that outputs 8-bit samples to a DAC. All code and data is in a 2048 byte ROM. I've now managed to disassemble and reassemble the ROM and figure out how parts of it works and even write my own replacement ROM with test sounds!
My newest Defender sound ROM plays a two-channel music loop, specifically a beepy version of the Lost Empire: Immortals theme.
This Sunday, I armed myself with a MC6800 manual and Visual Studio, and made a working Defender sound board emulator in C++. It currently only plays the boot sound, because I haven't implemented the full instruction set yet.