It changes by th embochure of your lips and the position that your slide is in. :)
Your lips are what vibrate when playing a trombone.
Let your lips flap a lot, and go to seventh flat position.
The trombone produces it sound by players buzzing their lips
A very short explanation is, you vibrate your lips while blow air through the mouthpiece. Pushing valves changes the length of tubing that has air going through it, causing different notes to sound.
The player's lips vibrate.
A slide...and their lips.
That's not the correct way to use it.
The position for high E flat on the trombone is third position. :)
they are all brass instruments but all have different pitches and different embouchures, such as the tuba is the lowest brass instrument and the trumpet is the highest and the trombone and french horn is in the middle, a tuba you have to have big lips to vibrate them loose and trombone and french horn too but you have to have tight lips for them and trumpet you have to have small lips and they all have valves except the trombone which has a slide to change pitch which makes it harder. (sorry if this was not the answer you wanted because i am a trombone player).
To play the trombone you press your lips together tightly and blow this creates a buzzing noise you do this into the mouthpiece.There ar seven positions on your slide.the tighter your lips the higher the note the loser your lips the lower the note. Keep trying its hard at first but then its EASY.
2nd position