No trumpet is built that plays in tune for all fingerings

Evidence

Adding lengths of tubing is almost exactly what the valves do, but, because of relatively sharp bends and slight discontinuities, the resonance peaks do not perfectly realign to each new fingering. No trumpet has been built that plays exactly in tune for all fingerings anywhere in its range. Small adjustments need to be made, by lipping notes up or down, or by tuning slides operated by fingers not used for pressing the valve keys. — Eric J. Heller, Why You Hear What You Hear- An…, 1565

Categorization

• SHARE: A brass-player friend would appreciate this: even the best trumpets need lipping and slide tricks because valve bends misalign resonances.
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 1565