Does this apply also to sax? I've listened to some (mainly old) recordings where the sax seems clearly out of tune; sometimes it's subtle but there are recordings in which it's so off that one wonders if it's done on purpose (1) and personally I really dislike it. Back in the day there weren't digital effects or they were so primitive that applying pitch correction on the fly while maintaining sound quality and spectral integrity was out of question, still tape recorders allowed to finely set their speed, so tuning the song to a sax being recorded would have been trivial.
As far as I know it applies to both brass and woodwinds, though the degree of difficulty involved probably varies between types of instruments and also (at least on the woodwinds I'm familiar with) note to note.
A sax is really easy to control (or lose control) of the pitch. And in fact, many saxophonists will just shift various ranges around sharp or flat to suit their style (cough Phil Woods cough).
So basically, a woodwind like a sax will tune a few notes with a piano or whatever, but it's really up to the player to keep playing in tune. I would not even bother trying to autotune or use post-processing; it'll just sound weird.
This is also how you can get a room full of student musicians "tuned" but it still sounds like a disaster.
retuning via tape velocity modulation would be easiest if the instrument in question was consistently out of tune with the rest of the band - like if the sax was always 15 cents flat relative to the harmonic structure.
usually that’s not the case though. typically it’s individual notes. much harder to precisely and accurately modulate tape velocity (especially by hand).
Yep. And - where musically appropriate - if you know which note of the chord you're playing, you can tweak the pitch towards the Pythagorean tuning and get the harmony to "ring" as the harmonics of each note reinforce each other.
This sort of hybrid tuning is common in barbershop quartet singing as well.
Also, the tubes for the individual valves have their own tuning slides. A trumpet will typically have a little thumb-operated lever for one of those slides, to help with some of the notes. I saw a video of a tuba solo, and the tubist was working the tuning slides almost as much as the valves.
Thumb-operated levers on trumpets are uncommon (though, IMHO ergonomically superior). More common are a ring in which you place your left ring finger. The ring is directly attached to a slide on the third valve, so you can flatten notes by extending your left ring finger.
Those removable slides are usually just to get the spit out of the loops. I haven't seen the lever you mention - are you sure you are not just looking at the usual [water key](https://www.youtube.com/watch?v=vMbb8-WK_VM)?
With valved brass instruments you are trying to approximate a logarithmic relationship with a linear sum of components. Trumpets have a high resonant Q, so not using the valve slides is going to produce out of tune notes. I played horn once upon a time. Horns have low resonant Q, so you just “lip it in”.
