What does “deep groove” mean?
If you’re interested in 50s and 60s jazz, you’ll probably encounter the phrase “deep groove” at some point, especially in relation to LPs on the Blue Note label. This can be confusing for beginning collectors who can easily misunderstand what “deep groove” means. “Deep groove” has nothing to do with the playable groove that holds the music. The groove that we’re talking about is one that can be seen on the label area. See that groove in the picture below? That’s what collectors call the “deep groove”.
Why are deep groove LPs so desirable?
Collectors use the presence of the deep groove to date LPs. After about 1960, the groove on the label area became less pronounced. If there’s a deep groove on the record, collectors assume it was pressed in the mid- to late-Fifties, so it’s likely to be an original pressing. For people who are looking for Blue Note jazz LPs from the hard bop period, this is the holy grail. For almost everyone else, it’s just a groove.
Although the deep groove is strongly associated with Blue Note, it is present on LPs from other labels as well. Here’s a great blog post on London Jazz Collector discussing the different grooves that you may encounter on late-Fifties jazz records, and here’s another one from the same site discussing the deep groove on Riverside LPs.
Where does the deep groove come from and where did it go?
There’s nothing magic or even very interesting about the deep groove. That groove was made when the record was pressed. If you pick an LP at random and look at the label area, you will probably see some similar ridges in the label area (although not as large or as deep). When a record is pressed, there is a part called a die that holds the stamper in the press. The die leaves a mark on the label area. Around 1960, the pressing plants that used those dies which left a deep groove on the label changed to using dies which left different marks, so the deep groove disappeared.