Much of tuning on a trumpet is done using the main tuning slide. Today, most bands and orchestras have tuners, which are machines that will register your instrument's sound and indicate to the musician if the note that is played is sharp (above pitch) or flat (below pitch). If the instrument is sharp, the musician should pull the main slide out. When it is flat, the slide should be pushed in. This is in accordance with the physics of brass. On average, the main slide should be pulled out from its housing about one half inch, to allow room to adjust either way.

Tuning is defined and set using the frequency of the note, in MHz (megahertz). The standard note from which most pitches are referenced is middle A, and middle A=440 MHz. There are some exceptions to the A=440 rule, because there are some bands that will as a whole tune to a slightly sharper pitch, such as A=442. When tuning a trumpet, most trumpeters will tune a middle G first, because it is a harmonic note, and generally will indicate the true tuning of the instrument. It is always a good idea to tune several more notes than just G, because each note has its own personality and feels just a bit different to play. Many times, tuning can be fixed by using an alternative fingering or just slightly changing the embouchere. For alternate fingerings, see the fingering chart. If a pitch is going sharp and you would like to correct it using your emouchere, open up your throat very wide, open your teeth, and relax to lower the pitch. If the pitch is flat, raise it by pushing faster air, supporting your diaphram, and raising your eyebrows.

This is an oberserved list of tuning tendencies for the range of the trumpet:

Note	Fingering	Tendency	Solution
		Flat	Support with air to hold pitch up
		Flat	Support with air to hold pitch up
		Flat	Support with air to hold pitch up
		Flat	Support with air to hold pitch up
		Flat	Support with air to hold pitch up
		Flat	Support with air to hold pitch up
		sometimes sharp	open mouth and teeth
		Very Sharp	Kick out 3rd valve slide all the way
		sharp	kick out 3rd valve slide 1/2 way
		OK	-
		sometimes sharp	listen. If sharp, kick out 1st slide a little
		OK	-
		OK	-
		OK	-
		OK	-
		sometimes sharp	listen. if sharp kick out 1st a little
		OK	-
		sometimes sharp	if sharp, lip down by relaxing embouchere
		sharp	open teeth, relax, support
		OK	-
		flat or sharp	listen carefully. If sharp, relax, if flat, use 13
		flat	Lip up, support with air
		flat	Lip up, support with air
		sharp	use 1st valve slide, open mouth
		often sharp	open mouth, relax
		very sharp	open up, or use 12 instead of open
	23	often sharp	kick out 3rd valve slide
		sharp	use 1st valve slide
		sometimes sharp	use 1st valve slide
		sometimes flat	support with air
		sometimes flat	support with air
		sometimes flat	if flat use 2
		sometimes flat	if flat, use open
		sometimes flat	if flat use 23
		OK	-