What Is This Technique For Clarinet?

Magnus Lindberg's Clarinet Concerto...Very striking technique - is it just a kind of overblown lip-bending glissando?

http://youtu.be/bzPI5z1cYvc?t=20m6s

overblown multiphonics probably. or one of the humming ones:

Thanks, that was pretty useful.

What is the best way to notate it - if I want to leave the fingering up to the performer?  Should I just write the fundamental, and a written explanation. Such as:

Multiphonic - gradual rise and fall of the harmonics across the written duration

Or something of the sort?  Does a bold capital "M" above the note work as well?  I think I've seen this?

Just saw this image, and it looks to describe in symbols what I wrote:  what do you think of this?

http://www.lutins.co.uk/thesis/images/bif-multi.png

Harmonic symbol with de/crescendos connected to it

Thanks again :)

you're welcome. thanks for the link. cool work. according to http://andrewhugill.com/manuals/clarinet/extended.html over the gliss you should write "growl" and the hummed notes in cue size, assuming that's the kind of multiphonics lindberg used.