Only one word can describe that: genius!
I don't think there is much more to say but for completeness the genius behind that video added this information when uploading it to YouTube:
No effects or sampling were used. What you see is what you hear (does that even make sense?):
Please note I had to record the HP scanner 4 separate times for each voice. I wanted to buy 4 HP scanners but for some reason sellers on E-Bay expect you to pay $80-$100, I got mine for $30. I keep hearing parts of the song are out of tune. Keep in mind the scanner and floppy drive are not musical instruments. These are mechanical devices whose motors tend to drift and can cause some notes to be out of tune.
- Atari 800XL was used for the lead piano/organ sound
- Texas Instruments TI-99/4a as lead guitar
- 8 Inch Floppy Disk as Bass
- 3.5 inch Hard Drive as the gong
- HP ScanJet 3C was used for all vocals