xline~ is an extension of the line~ object with the possibility to control the curve from linear to logarithmic.
Borg Manual :
Left-top inlet <- your sound, EX: an oscillator.
Middle-top inlet <- a value in the range [0-1] that is a volume control.
Right-top inlet <- a value in the range [1-8] that is the curve control.
Bottom-left outlet <- your output from the xline~ object.
object download :