A couple of examples of extended practices explained and demonstrated with examples on when to use the particular sounds.
Quartertones and Microtones
Intervals smaller than a semitone. Notations vary, but the examples shown seem typical of quartertones and raised & lowered inflections. Microtones may be produced either by lip bend or with the hand (although that changes the timbre as well as the pitch).
singing and playing into the instrument simultaneously. write the sung notes in small noteheads and/or verbal instruction - sing into instrument. Multiphonics are possible on the horn but not commonly used.