Lesson 2 of the altissimo course is long tones. There are some long tones in the daily routine as well but not as many. this is very important stuff and long tones are often overlooked by students because they are so boring. boring yes but if you do them as instructed like with all the different degrees of volume (this is key), it will help your breath control and that is a major way to improve your tone.
Keep at it JB!