Brazilian 7-String Guitar Tuner

A classical guitar with a low C underneath it

The violão de 7 cordas is tuned C2–E2–A2–D3–G3–B3–E4, read from the seventh string to the first. Everything from the sixth string up is a classical guitar and stays exactly where you left it; the whole instrument is one string added below, at C2, 65.41 Hz. That is lower than any note on a six-string and only four semitones above the open E of a bass guitar.

Why C rather than B, when B is the tidier interval? Repertoire. Choro and samba are written overwhelmingly in C, D, F, G and A, and hardly ever in B or E — so an open low C is a note you can actually use, and an open low B mostly is not. That decision was made in the 1950s by Dino Sete Cordas, who reached it the practical way: he fitted a cello string to a guitar and tuned it to C, and played it with a thumb pick to get it through the microphones of the day.

What the string is for matters as much as where it is tuned, because it is not a drone. The seventh string carries the baixaria — the descending contrapuntal bass lines a seven-string plays between the melodic phrases, answering the flute or the bandolim rather than accompanying it. That is why the note choice is about which scale runs sit comfortably under the hand, not about which chord roots you can reach.

C, B or A: what one seventh string will actually take

All three turn up in real playing, and a single string is usually rated for all three — the Savarez seven-string set, for instance, specifies its seventh for A, B and C. What changes is tension, and the arithmetic is steep, because tension climbs with the square of frequency. On that set the seventh pulls about 10.1 kgf at C2, roughly 8.9 kgf at B1, and only 7.1 kgf at A1. Dropping from C to A throws away nearly a third of the tension on a string that was not tight to begin with.

That is what you hear when a low seventh goes wrong: not a wrong note, but a slack one — buzzing against the frets, reading sharp for the first instant of a firm pluck and then falling back, and intonating poorly up the neck because a floppy string stretches proportionally more when you press it down. If you play in B or A regularly, the fix is a heavier seventh, not a tighter turn of the peg. A common nylon seventh such as D’Addario’s is around .056″ and is specified for the B-to-C range.

Tuning routine, and the fret check that proves the seventh

1. Set the six upper strings before anything else, treating the instrument as an ordinary classical guitar. They are unchanged, the dial locks onto them faster than it locks onto the bass, and once they are right they become the reference the seventh gets checked against.
2. Mute everything else before you touch the seventh. Lay your palm across the other six. A low C sets sympathetic strings ringing, and a tuner asked to choose between two sounding notes will hunt between them.
3. Pluck the seventh gently, with flesh rather than nail, and wait. At 65 Hz the detector needs several full cycles before it can commit. Give the note a second or two and read it once it has settled rather than during the attack.
4. Approach from below. Come up to pitch rather than down to it. Nylon and a tuning machine both have slack, and a string you stopped while loosening will keep drifting flat for the next few minutes.
5. Confirm it against the sixth string with a fret. With the seventh in C, the 4th fret of the seventh string is the open sixth string — C2 plus four semitones is E2. Play them one after the other and they must be the same note. If you have retuned the seventh to B, that check moves to the 5th fret; in A, to the 7th fret. Getting it right at the wrong fret is the usual sign that the string is not where you think it is.
6. Go round once more. On a new set of nylon, go round several times over several days.

Three different instruments called a seven-string guitar

The name collides across three traditions, and the tunings have almost nothing to do with one another:

• Brazilian, C2–E2–A2–D3–G3–B3–E4. Nylon (or the older hybrid steel set), a 650 mm classical scale, played fingerstyle for baixaria in choro and samba. This page.
• Extended-range, B1–E2–A2–D3–G3–B3–E4. Steel-strung electric, a 25.5 to 27 inch scale, the low string there for riffs rather than counterpoint. It is one semitone below the Brazilian seventh and a different instrument in every other respect — our 7-string guitar tuner covers that one, including why the low B goes unstable on a short scale.
• Russian, D2–G2–B2–D3–G3–B3–D4. An open G major chord, built in thirds rather than fourths, developed around Andrei Sychra in the early nineteenth century for Russian romances. None of the Spanish-guitar shapes apply at all.

Any of the three reads fine on the dial above, which names notes rather than assuming a preset. What no tuner can do is guess which of the three instruments you are holding, and the single semitone between C2 and B1 is a small enough gap that a display showing only letters will happily let you spend an evening on the wrong one.

Steel, nylon, and what the school actually plays

There is no single correct string material here, which surprises people who expect a classical guitar. The traditional samba instrument that Dino played is steel-strung, and hybrid: nylon on the 1st and 2nd strings, steel on the other five. It is loud, it cuts through a roda, and the nylon trebles keep the top end from turning brittle. From the 1980s a fully nylonseven-string took over in choro and is what most contemporary players and conservatories use; Raphael Rabello’s playing from the late 1970s onward is the reason a generation went looking for one.

For tuning purposes it makes no difference — C2 is C2 either way. It changes two practical things: which set you buy, since a steel hybrid and a nylon set are not interchangeable on the same instrument, and how long the strings take to settle, since nylon creeps for days where steel is mostly done inside an hour.

What the needle can tell you, and what it cannot

Everything here is measured against equal temperament — the same grid your fret slots were cut to, which is why a string set by this dial agrees with itself once you stop it at the fifth fret. Two limits are worth knowing on this instrument in particular.

The first is the low C itself. Wound bass strings are not perfect harmonic oscillators — their overtones sit slightly above exact multiples of the fundamental, and the effect grows with the mass of the winding. So a seventh string tuned dead centre by its fundamental can still sound a shade flat against the rest of the instrument, and many players leave it a cent or two sharp on purpose. Nothing is misreading: the fundamental is being measured exactly right, and it is your ear that weighs the overtones stacked on top of it. Our guide to cents covers the size of that gap.

The second is the baixaria itself. Those lines are played on the wound strings, low on the neck and often with a firm attack, and that is where fretting pressure and string stretch push pitch sharp by an amount no open-string reading can predict. Tune the open strings with the dial, then play an actual descending phrase and listen — if it sounds sharp while every open string reads centred, the answer is in your left hand or in the instrument’s setup, not in the pegs.

Frequently asked questions