For example, the third in a major triad is flattened, while in a minor triad it is raised. The fifth in a major triad is raised, while in a dominant seventh chord the seventh is lowered. Scan the parts of any good orchestra trombone section and numerous up and down arrows will be found indicating the positions of key notes in the harmony. The best players leave little to chance. There are intonation problems built into the trombone at the factory.
Every instrument is a compromise, as fixing one area exaggerates the difficulties somewhere else.
Instrument makers try to come up with what they feel is the best possible combination of good traits. To play in tune you need to be aware of the present situation. Play the notes in the head and the slide will automatically go where it must to reproduce those sounds. Listen to the bass, and tune the notes in your head with the orchestra's foundation. The tuning note given at the beginning of a performance has little value for intonation.