inserting ramp into signal

I have a function object controlling the amplitude envelope of a sound. I want to play the sound with variable rhythms, but when the rhythm changes are shorter than the domain length of the function, I get clicks when the function jumps back to its beginning. I'd like to insert a short ramp so that the jump from the last value to the first is softened. I assume I need to use a line~ object at some point in the signal path, but I'm not sure where to put it. Any help would be much appreciated!