“Some copies of this 10” have “hand carved lock grooves”...
http://www.stereolab.co.uk/discography/SINGLE/8/8SIRE11.jpg
o my freekin god!!! this is one of the things i did in mom’s basement back circa ‘77, scraping the inner groove of records with my xacto knife. i got one of them to make a sound that was sorta scratchy but suggested the words ‘pink potatosack pink potatosack pink potatosack etc.’
the most famous lock groove, if i remember rightly, is the sergeant pepper one with the laughing people.