Play the note written as C on an alto saxophone, with the fingering for C, reading music that says C — and a piano playing along will tell you that you are, in fact, playing E♭. Nobody is wrong. Your part is right, your fingering is right, and the piano is right. You are meeting transposition, the single most confusing idea in a beginner's first year, and this guide explains it the way it should have been explained the first time: slowly, with the reason why.
The one-sentence version
A transposing instrument is named after the note you hear when the player reads and fingers a written C. An alto saxophone is "in E♭" because its written C sounds E♭. A B♭ clarinet's written C sounds B♭. A flute is "in C" because its written C sounds C — which is another way of saying it does not transpose at all.
That is the whole definition. Everything else is arithmetic and history.
Why would anyone design that?
Because of families and fingers. Saxophones come in sizes — soprano, alto, tenor, baritone — and Adolphe Sax wanted a player to pick up any of them and read the same music with the same fingerings. So every saxophone's part is written as if the instrument were the same size: the fingering for written B is the left index finger on all of them. The cost of that convenience is that the sounding pitch differs by size: the bigger tube sounds lower. Rather than make players relearn fingerings per size, music publishers move the written notes instead. The player's part is transposed so that the fingerings stay constant and the sounds come out right when everyone plays together.
The same logic runs through clarinets (mostly in B♭, some in A), trumpets (B♭), horns (F) and the rest of the saxophone family. It is not a conspiracy against beginners; it is a kindness to doublers that beginners pay for in confusion for about one school term.
The intervals, instrument by instrument
The gap between written and sounding pitch is fixed for each instrument:
- Alto saxophone (E♭): sounds a major sixth lower than written. Written C → E♭ below it. Written G → B♭. To find concert pitch from an alto part, count down six letter names (or up a minor third — same note, easier maths for many people). - Tenor saxophone (B♭): sounds a major ninth lower — an octave plus a whole tone. Written C → B♭ an octave-plus below. - Soprano saxophone (B♭): sounds a major second lower. Written C → B♭. - Baritone saxophone (E♭): same interval as alto, one octave lower again: written C sounds E♭ two octaves-ish down (a major sixth plus an octave). - Clarinet (B♭): sounds a major second lower. Written C → B♭; written G → F. (Our clarinet note pages show this on every page: written E3 sounds D3.) - Trumpet and cornet (B♭): a major second lower, like soprano sax. - French horn (F): sounds a perfect fifth lower. Written C → F below. - Flute, piccolo, oboe, bassoon, trombone, tuba, euphonium (bass clef): in C — written = sounding. (Euphonium and baritone horn in treble clef are the exception that catches everyone: their treble parts are written a major ninth above sounding pitch, B♭-style. Our euphonium note pages show both names for exactly this reason.)
Every note page on this site lists the concert pitch next to the written note — on the saxophone pages, for all four family members at once — so you never have to do this arithmetic at a rehearsal desk.
The two directions (where everyone gets lost)
"The band is playing a concert B♭ scale. What do I play?" Work backwards: you need the written note that sounds B♭. Alto (down a major sixth to sound): written G sounds B♭... check: written G on alto sounds B♭ a sixth below — yes, G is your note. Clarinet (down a tone to sound): written C sounds B♭ — play C. Trumpet: same as clarinet, play C. Horn (down a fifth): written F sounds B♭... written F down a perfect fifth is B♭ an octave below — play F. Flute: play B♭. This is why the band director's "concert B♭" produces five different written scales around the room, and why warm-ups sound like chaos for the first ten seconds.
"My part says A. What will the audience hear?" Work forwards with your instrument's interval. Alto: A down a major sixth = C. Tenor: A down a major ninth = G. Clarinet: A down a tone = G.
A memory hook that survives: the instrument's key name is what C sounds like. "In E♭" = C sounds E♭. "In B♭" = C sounds B♭. "In F" = C sounds F. If you know what your C does, you can rebuild everything else by counting.
Why your tuner "disagrees" with your sheet music
Tuners and piano apps hear concert pitch. Play your written A into a tuner: alto shows C, tenor shows G, clarinet shows G — and the tuner is telling the truth about the sound. Beginners regularly conclude their instrument is broken or their fingering is wrong; neither is true. (One more worked example, because it surprises everyone: written B♭ on alto sounds D♭ — count down the major sixth: B♭, A♭, G, F, E♭, D♭.) When you tune in band, you tune to a concert note the director names, and you play the written note that produces it — for the usual concert B♭, alto plays written G, as worked out above. Tuners with a "transposition" setting exist precisely for this; set yours to E♭ (alto/baritone), B♭ (tenor/soprano/clarinet/trumpet) or F (horn) and it will display written pitch instead.
A worked example to keep
Your band is playing a piece in concert E♭ major. The piano's scale runs E♭–F–G–A♭–B♭. Your alto part shows a scale too — but written in C major: C–D–E–F–G. Play it exactly as written, and what comes out is every note a major sixth lower: E♭–F–G–A♭–B♭ — the band's key, produced from a part with no flats in its key signature at all. The same relationship holds everywhere: a concert B♭ piece arrives on the alto stand in G major, a concert A♭ piece in F major. Real parts confirm the arithmetic every rehearsal.
The pattern worth memorising is not any table — it is the method. Work from the concert note you need to the written note that produces it, using your instrument's interval (for alto: the written note sits a major sixth above the concert note). Then sanity-check with the C-rule: written C sounds the instrument's key name — E♭ on alto. If your interval maths says the alto part for concert E♭ is in C major, the C-rule agrees instantly (written C is concert E♭ on alto), and you can trust it. Two independent routes to the same answer is how you stop getting transposition wrong in public.