Sal's holotape is a holodisk in Fallout 4.
Location
It can be found on the body of Sal at Jamaica Plain's destroyed town hall on the 2nd floor.
Transcript
Damn it. Worthless bastards. Scattered like radroaches the moment they saw their first Ghoul. I've spent months prepping for this op. There's no way I'm backing out now. That treasure will be mine. Even if I have to dig it up with my own bare hands.
Related quest
Listening to the tape starts Find the Treasures of Jamaica Plain and adds a map marker for Jamaica Plain.