Two queries

1) Any useful books on modern techniques like multiphonics, glissandos etc etc etc?
2) Is Herberle REALLY that hard to pull off successfully compared to say Bruggen?

Hi I L. A useful one is by Walter Van Hauwe and is called Modern Recorder Player. You need volume three. . Published by Schott and well worth having in your library.

I second this suggestion it really is a useful reference for all aspects of recoder playing not just the extended technique aspects. Do get all 3 volumes, you will probably look at Vol 1 and dismiss it as too basic but it really does have some very valuable material.