We’re not talking about scales though. We’re talking about the difference in transposition of one instrument to another. A scale is just a group of notes that adds up to a tonality. Like a major scale has a certain sound to it, and a minor scale has a different sound. Even C major and A minor have a different sound (tonality) from each other, even though they have the same notes.

Still concert A (440 vibrations per second) on the guitar transposed to a horn instrument should be the same sound in pitch. Regardless of the system of notes it contains, or distance between each pitch. If it didn’t, all music would sound horrible cause everything would be terribly out of tune. And these distances aren’t too much of a factor because no instrument plays an A note that vibrates at exactly 440 vibrations per second. Even the way you pluck a string on your guitar cause the A note to waver around 440 vbs. You can notice this on a tuner cause it will usually waver ever so slightly, depend on its accuracy. Luckily no human ear is perceivable enough to noticing this difference. Every pitch that sounds in the vicinity of 440 vbs. would sound like an A, regardless of instrument. If it strays to low and sort of in between A and Ab than a cultured ear would notice it being a mix between the sound of A and Ab. Although that is out of tune, and it wouldn't sound good with anything. I think the difference in key between instruments (Bb clarinet) already makes up for this difference in the distance between notes.

I believe you man, but it's not a difference to where it would cause both instruments playing an A to sound that bad. More than likely it was a Tenor Trombone, or an Alto Trombone. Which there was a confusion between notes, but regular trombones are still in Concert Pitch.