In "Homestuck -- Sheet music by Miff (based on Homestuck Anthem) -- MIDI by Miff", the MIDI link leads to https://miffthefox.info/misc/mspa/homestuck.mid, which 404s. Based on the sheet music link leading to miffthefox.info/mspa/ rather than miffthefox.info/misc/mspa/, I tried changing the URL to https://miffthefox.info/mspa/homestuck.mid, and it worked.
In "Homestuck -- Sheet music by Miff (based on Homestuck Anthem) -- MIDI by Miff", the MIDI link leads to https://miffthefox.info/misc/mspa/homestuck.mid, which 404s. Based on the sheet music link leading to miffthefox.info/mspa/ rather than miffthefox.info/misc/mspa/, I tried changing the URL to https://miffthefox.info/mspa/homestuck.mid, and it worked.