Shifting the start of a tie

[Urs Liska]

The attached PNG shows the upper two ties colliding with the stem of the 
second voice.

Is there a way to make the ties shift their horizontal starting position 
(but not the end), without using \shape?

I can imaging having all three ties of that voice start on the same X 
position, but I don't know how I could address the ties individually to 
apply \shape through the edition-engraver in this context.

Any suggestions?
Thanks
Urs

encore.png
Description: PNG image