Two horns, one bell, and an order that matters
A double horn is not one instrument with an extra button. It is an F horn and a B♭ horn sharing a bell and a set of valves, with a thumb trigger that swaps which set of tubing the air goes through. Each side has its own length, its own harmonics, and its own idea of what is in tune.
Which means there are two slides to set, and — this is the part almost everyone gets wrong — a fixed order to set them in:
- Tune the B♭ side first, using the main tuning slide.
- Then tune the F side, using the F slide. Do not touch the main slide again.
The reason is plumbing rather than tradition. On almost every double horn the main slide sits in the air path of both instruments, while the F slide sits in the F path only. Set the F side first and then reach for the main slide to fix the B♭ side, and you have just moved the F side back out. Do it in the correct order and each adjustment stays where you put it.
A horn that is permanently almost right — one side always a little off no matter how often it is tuned — has usually been tuned in the wrong order for years.
The first tab is what you actually sound for the common tuning calls; the second is how those same notes look on your part. Compare them once and the transposition stops being confusing.
The fifth between the page and the tuner
A horn in F is a transposing instrument: written pitch sounds a perfect fifth lower. Your written C is concert F. That single fact accounts for most horn players’ complaints about tuners, because the display is naming the note in the air while the page names the note under your fingers, and both are correct.
| The director says | You play (written) | The tuner shows |
|---|---|---|
| Concert F | C | F · 174.61 Hz |
| Concert B♭ | F | A♯/B♭ · 233.08 Hz |
| Concert A | E | A · 220.00 Hz |
| Concert E♭ | B♭ | D♯/E♭ · 155.56 Hz |
Written third-space C, sounding concert F, is the traditional note to tune on, and it earns the tradition: it is comfortably in the middle of the range and it exists on both sides of a double horn, so you can flip the thumb trigger and compare the two directly without changing anything else.
Tuning routine
- Warm the instrument properly first. Long tones, a few slurs, several minutes. A horn holds a lot of tubing close to your body and it warms unevenly; anything set cold will be sharp later.
- Empty the water. Condensation collects fast in a horn and a slug of it in a slide changes both pitch and response. Do this before you conclude anything is out.
- Thumb down for the B♭ side. Play your tuning note. Set the main slide. Steady dynamic — do not crescendo into it, because brass pitch rises with volume and you will tune to a note you never actually play.
- Release the thumb for the F side. Play the same written note. Set the F slide. The main slide is now finished with; leave it alone.
- Flip back and forth on that one note and listen for a step in pitch as you change sides. There should not be one.
- Check again after the first piece, and at the interval. A hall with an audience in it is warmer than the one you rehearsed in.
What the hand is for
The horn is the one brass instrument with a continuous pitch adjustment built into normal technique: the right hand in the bell. Closing the hand slightly lowers the pitch, opening it raises it, and experienced players do this constantly without thinking about it.
For tuning purposes that is both useful and a hazard. Useful, because it is how you place a note that the valves cannot fix. A hazard, because it means you can unconsciously correct a badly set slide and never discover the slide was wrong. When you are setting the main slide, keep the hand in its normal playing position and resist the urge to help — you want the slide to be right when the hand is neutral, not when it is compensating.
What the needle can and cannot settle
The dial does two things well here: it sets the two slides against a fixed reference, and it shows you your instrument’s own tendencies. Everything after that is ensemble playing, where the horn section spends most of its time holding the middle of chords — and a chord locks when its third is lower than equal temperament puts it, not when every player is centred on a dial. If the section sounds better after everyone stops looking at their tuners, that is not a coincidence; our guide to cents covers why. Elsewhere in the brass, the trumpet tuner shares the transposition problem a fourth away, and the tuba tuner deals with the same slides at the other end of the range.
Frequently asked questions
Which slide do I tune first on a double horn?
The B♭ side, using the main tuning slide — then the F side, using its own F slide. The order is not a preference, it is forced by the plumbing: on almost every double horn the main slide is in the air path of both instruments, while the F slide is in the F path only. So if you set the F side first and then move the main slide to fix the B♭ side, you have just undone the F side. Do it the other way round and each adjustment stays put. A horn that is permanently almost in tune has usually been tuned in the wrong order.
Why does the tuner never show the note I am playing?
Because the horn is in F and your part is transposed. A written C on a horn part sounds a perfect fifth lower — concert F — so the tuner is naming the pitch in the air while the page names the pitch under your fingers. Neither is wrong. When the band tunes to concert B♭, that is a written F for you; when an orchestra tunes to concert A, that is your written E. Do the conversion once at the start of a rehearsal and the display stops being confusing.
What note should I tune on?
Written third-space C — sounding concert F — is the traditional choice, and it is a good one because it is in the middle of the horn’s comfortable range and it is available on both sides of a double horn, so you can compare them directly. Whatever you choose, use the same note every time and play it at a normal dynamic. Brass pitch rises with volume, so tuning on a note you push and then playing at mezzo-forte leaves you flat all evening.
My F side and B♭ side disagree on the same written note. What now?
That is exactly what the two slides are for, and it is why the tuning order matters. Set the B♭ side with the main slide, then bring the F side to match with the F slide, comparing the same written note on each. If they still refuse to agree after both slides are set, the usual causes are a leaky change valve, condensation in one side, or a slide that has been pulled so far it is barely gripping. It is a maintenance question at that point rather than a tuning one.
Do I need to warm up before tuning?
Yes, and the horn is more sensitive to this than its size suggests, because so much of the tubing is wrapped close to the body and warms unevenly. A cold horn plays flat and rises as warm air passes through it, so anything you set in the first minute will be sharp by the tenth. Play some long tones and a few slurred intervals first, then tune. If the hall temperature changes during a concert — and it does, once an audience is in it — expect to nudge the main slide at the interval.