Difference Between - (Minus Sign) and Chassis Ground in Schematics
Op-Amps come in two forms. Single Rail/Supply, and Dual Rail/Supply.

Your op-amp, the NE5532 accepts +15V to -15V, and can be used in a single or dual supply mode:




Single Rail are typically Positive Voltage to Ground reference, while Dual Rail op-amps typically have Positive to Negative.

Single Rail are more common in newer, DC based designs, while Dual Rail are older, or AC designs.

Typical Audio is an AC signal, swinging above and below the ground reference. Single Rail designs cannot swing below it's low side reference. At best, you can add a DC offset and a virtual ground.

In your case, it's plainly a dual rail op-amp, with VCC- meaning the negative voltage rail of the power supply.

It will often be matched by a dual rail transformer:



This one uses a center tap between the two rails as the ground reference.

See http://www.talkingelectronics.com/projects/OP-AMP/OP-AMP-1.html for more information.