tetris-update-speed-function

tetris-update-speed-function is a variable defined in `tetris.el'.
Its value is

tetris-default-update-speed-function

• This variable may be risky if used as a file-local variable.

Documentation:
Function run whenever the Tetris score changes.
Called with two arguments: (SHAPES ROWS)
SHAPES is the number of shapes which have been dropped.
ROWS is the number of rows which have been completed.

If the return value is a number, it is used as the timer period.

You can customize this variable.