https://www.wothke.ch/tinyrsid
My WebAudio based C64 music hardware emulator is the root of this particular experiment. The pages are done using Joomla with custom MySQL/JavaScript/jQuery/CSS/AJAX thrown in for special purpose GUI functionality (like the one in the sceenshot).
At its core the page uses my (meanwhile) WebAssembly based WebSid emulator that allows to play C64 music using the original C64 binaries. To achieve this the emulation performs a clock-cycle exact simulation of the respective C64 hardware (e.g. MOS 6510 CPU, MOS SID sound chip, CIA timers, VIC II video chip).
update: In 2018 Jens-Christian Huus created a similar functionality page https://deepsid.chordian.net/ that also allows to browse the various releases of the High Voltage SID Collection (HVSC) and play respective songs online using my WebSid emulator. Contrary to my page here that page is regularly updated and I’d recommend it to any C64 music enthusiasts that haven’t heard of it yet.