Playing the saxophone double tounging overtone technique

[saxn00b445]

not sure what to call it but a lot of players like eddie lockjaw davis for example often do this technique where they play two notes dooden tounged or ghost tounged and the second note comes out way brasher like an overtone, not sure if its a false fingering or just a way of attacking the note

View: https://youtu.be/ROOTf-DDr8Y
this is a direct example of someone doing it. at the end of this 3 second clip they do the technique
does anyone know what this is called and how to do it?

 

[Pete Effamy]

It's the low C fingering used and allowed to "break up" a bit. Sounds like a C anyway, without checking..