Measurements and calculations of the input impedance of wind musical instruments are now well mastered. The purpose of this work is to study experimentally how far the resonance frequencies of brass instruments, taken from their input impedance, are able to give informations about the playing frequencies. Three different trumpets, obtained by changing only the leadpipe of the same instrument, were considered for the experiment. After a measurement of the input impedance of these trumpets, four musicians were asked to play the five first playable notes (regimes 2 to 6), for four different fingerings. This exercise was done for three nuances and was repeated three times. Finally, these 3×4×5×4×3×3=2160 notes allow us to make a quantitative assessment of the relations between the resonance frequencies and the playing frequencies. Results show first, a limited influence of the musician on the overall intonation of the instrument. Second, the pitch of the notes does not vary much with the nuances. Finally, the results confirm the fact that variations of the resonance frequencies lead to variations of the playing frequencies of the same order.