The Tri-sound switch is the name Ibanez applied to a type of pickup modification.
The Tri-sound switch allows the player to access multiple "voices" of a humbucking pickup:
- as a serial-connected humbucker,
- as a single coil,
- as a parallel-connected humbucker.
Both the neck PU and the bridge PU may have their own independent switch, on top of the usual 3-way switch.
The feature is found on several Artist models, be it the solid body AR series or the semi/full hollow body Artstar series. It was introduced in the late 70's (for example the Ibanez PF-300 in 1978 or the MC-300 in 1979).