Here is how I do it.
How I make a coyote howl. It is difficult to explain in words how to make a greeting howl, but I will give it a try. The greeting howl is 2 or 3 barks followed a 2 to 3 second high pitched howl. It takes a lot of practice to get it right. To make the two or three barks at the start you put about 80% of the Dan Thompson Red Desert mouthpiece in your mouth (with the reed up) and do a sharp fast "huff" into the call and at the same time you pull the mouthpiece out of your mouth about a quarter of an inch. The long howl at the end starts like a bark, but you pull the mouthpiece out of your mouth about half way and squeeze on the reed to make the pitch go higher. The challenge bark has the 2 or 3 barks followed by a high pitched howl for about 1 second. During the short howl, the pressure is varied to make the variable pitch during the howl. Hope this helps.