Manually set slur points

[Elmo Todurov]

I'm amazed with LilyPond. I've done several pieces of sheet music with it and 
I'm still amazed. It's not a tool, it's an instrument.

Here's my problem: I want to make a "custom" slur that would squeeze through a 
small space between two chords.. irrelevant. I want to make a slur with more 
than 2 curves. The current code allows to create custom slurs in the form 
of "moustache", so that both ends turn in the same way or vice versa, so that 
one end turns up and the other down. I want to add a third curve in the middle, 
so that the slur would look like M.

The program reference 
http://lilypond.org/doc/v2.9/Documentation/user/lilypond-internals/Slur.html
wasn't helpful at all -- it only stated that it's possible. LilyPond snippet 
repository told me the right way to do this, but it uses only 4 referencre 
points (when I strip it to 3, it connects to (0 . 0) and so makes a loop). I 
want at least 5 points. Is it currently possible? Is it theoretically possible 
(I'm not familiar with Bezier curves)?

Kudos for the excellent job,
Elmo