Here are some links to interesting pages, inclduing masterclasses and articles about playing:

The legendary horn player Hermann Baumann talks about the subject of singing and playing ....

Arnold Jacobs

Arnold Jacobs (June 11, 1915 - October 7, 1998) was an American orchestral tuba player who was most known as the principal tuba player for the Chicago Symphony Orchestra from 1944 until his retirement in 1988.

Jacobs was considered one of the foremost brass pedagogues of his time and was considered an expert on breathing as it related to brasswind, woodwind, and vocal performance. Due to childhood illness and adult onset asthma, his lung capacity was significantly impaired. He is best remembered for his playing philosophy which he referred to as "song and wind".

Follow the link below to find a selection of clips from his lectures and masterclasses:

Arnold Jacobs Masterclasses

A fantastic website by a brilliant horn-player and complete horn-nut

Pip Eastop

Well worth a look. 

Full of interesting and entertaining articles about horn-playing