Change print-appearance of chord members to different duration, but not the logic behind.

[Nils]

Hello,

The goal is to have a very simple way of creating mixed-duration chords.I do 
not know of any way to do this in lilypond which does not involve different 
voices.

So I want to change single notes in a <chord> so that they appear as different 
duration, but only as printed item. The duration of the whole chord, 
Measure-calculation etc. should not be affected by this.

Is there some override to achieve this? 

Nils