The Harpsichord Tile Shifting Effect is a nice way to illustrate how Ultima V manages tiles. Playing "Stones" on Lord British's harpsichord in Ultima V opens up the secret passage to the Sandalwood Box. However, getting out the mechanism behind the vanishing of the wall gives quite amusing results.
It is important to know that all tiles of Ultima V are stored in a list. Basically, playing the harpsichord tells the game that the tile X (the wall tile in question) is to be replaced with a tile so many places down the list, which in case of the wall is a free floor. Playing the harpsichord again returns the floor to a wall, since the command now is to go an equal amount of places up the list.
Of course knowing this, the mechanism can be abused in quite a number of ways, after opening the wall:
- Pushing the potted plant into the gap and then playing "Stones" turns it into crendellations.
- Pushing a southward facing chair into the gap turns it into closed portcullis.
- Pushing a northward facing chair into the gap turns it into a table with food. Eating the food and then again playing the harpsichord turns the empty table into a mirror with reflection (it is a different tile from a normal mirror).
- Leaving the Magic Carpet on the spot and playing the harpischord will leave the carpet there, but block the view to the room behind the wall. You can move on the carpet, but if you pick it up, the normal wall will remain in that spot and you can accidentally trap yourself in Lord British's secret room.
It must be stressed that the changing of tiles isn't anything unusual in Ultima V. It merely depends on the trigger and the number of places the tile is shifted on the tile list. This for example is used when opening the dungeons, down to profane things like walking in front of a mirror. The harpsichord is only unusual in the aspect that it can be misused to morph objects, something the programmers clearly didn't intend.
Below a video of the harpsichord effect and how it can be misused.