bass clef: which line do the two dots mark?
A bass clef is an F clef. Two dots sit on either side of the fourth line, so that line is F3. From the bottom, the five lines read G2, B2, D3, F3, A3. Recomputed with A4 = 440 Hz, F3 is 174.61 Hz. On 21 October 2026 this site’s key finder read a 24-second prelude written on this staff as G major, Camelot 9B, at 76%.
What the two dots fix
Wikipedia’s Clef article, read on 21 October 2026, says the bass clef is the F clef that places F3 on the fourth line. That line runs between the two dots. F3 is the F below middle C. Middle C is C4.
Count upward from the top of this staff and middle C lands on a ledger line above it. Top line A3, space above the staff B3, then one ledger line: C4. The same article’s drawing of middle C on the bass staff puts it there. C4 recomputes to 261.63 Hz.
The same article lists cello, double bass, bass guitar, bassoon, trombone, tuba, and timpani among the parts that read a bass clef. It is also the lower staff of the piano. The article says double bass, bass guitar, and contrabassoon sound an octave lower than the written pitch. A written F3 for those three is the pitch an octave under the F3 this page calculates. The article does not give the cello that drop. The clip below is the opening of a solo cello suite. The recording’s own file page does not name the instrument in its description.
The five lines and four spaces
The same Clef article, still the 21 October 2026 reading, prints two sayings for this clef. Lines, bottom to top: “Good Boys Do Fine Always”, G B D F A. Spaces, bottom to top: “All Cows Eat Grass”, A C E G. Those two sentences are the article’s mnemonics, not a second source.
| Line | Pitch | Hz | Saying |
|---|---|---|---|
| Bottom | G2 | 98.00 | Good |
| 2nd | B2 | 123.47 | Boys |
| 3rd | D3 | 146.83 | Do |
| 4th | F3 | 174.61 | Fine |
| Top | A3 | 220.00 | Always |
| Space | Pitch | Hz | Letter |
|---|---|---|---|
| 1st | A2 | 110.00 | A |
| 2nd | C3 | 130.81 | C |
| 3rd | E3 | 164.81 | E |
| 4th | G3 | 196.00 | G |
Numbers you can check
Equal temperament, A4 = 440 Hz, sets a pitch at 440 × 2((midi − 69) ÷ 12) Hz. The five lines, bottom to top:
G2 is midi 43: 440 × 2((43 − 69) ÷ 12) = 440 × 2(−26 ÷ 12) = 97.998… Hz, which rounds to 98.00 Hz.
B2 is midi 47: 440 × 2((47 − 69) ÷ 12) = 440 × 2(−22 ÷ 12) = 123.470… Hz, which rounds to 123.47 Hz.
D3 is midi 50: 440 × 2((50 − 69) ÷ 12) = 440 × 2(−19 ÷ 12) = 146.832… Hz, which rounds to 146.83 Hz.
F3 is midi 53: 440 × 2((53 − 69) ÷ 12) = 440 × 2(−16 ÷ 12) = 174.614… Hz, which rounds to 174.61 Hz. That is the line between the two dots.
A3 is midi 57: 440 × 2((57 − 69) ÷ 12) = 440 × 2(−12 ÷ 12) = 220 Hz exactly, 220.00 Hz.
G3, the top space, is the G that sits inside this staff. It is midi 55: 440 × 2((55 − 69) ÷ 12) = 440 × 2(−14 ÷ 12) = 195.997… Hz, which rounds to 196.00 Hz. That is the tonic octave used for the G major reading below. It is arithmetic, not a frequency measured off the recording. C4, the ledger line above this staff, is midi 60: 440 × 2((60 − 69) ÷ 12) = 440 × 2(−9 ÷ 12) = 261.625… Hz, which rounds to 261.63 Hz. On 21 October 2026 this site’s key finder called the opening of Bach’s G major cello prelude G major at 76% confidence.
A recorded example you can check
Wikipedia’s article Cello Suites (Bach), read on 21 October 2026, names “Suite No. 1 in G major, BWV 1007” and describes the set as unaccompanied cello. The first page of the Anna Magdalena Bach manuscript, Commons file Bach1sa2.PNG, opens with a bass clef, one sharp, the word “Prelude”, and “Suite 1”. Wikipedia presents that image as her copy, not as Bach’s lost autograph. The work list names G major. The ink shows a bass clef and one sharp. One sharp is the usual signature of G major. The two pages do not copy each other: one is a work list, the other is a manuscript copy.
On 21 October 2026 at 10:40 EDT this site’s key finder read this 24-second clip as G major, Camelot 9B, at 76% confidence, with the hint “Check against your audio”. It listed D major (Camelot 10B, 6%) and G minor (Camelot 6A, 6%) next. The screen did not add a low-confidence note. That percentage is the finder’s estimate for this file, not a measured accuracy rate. The work list names the suite G major, and the finder named G major as well.
What our key tools tell you
Give a recording to the key finder for the key it hears. The two dots are read from the staff, not from that percentage. A bass clef still marks F3 on the fourth line when a short clip comes back under some other name. Where the sharps or flats sit after this clef is a different question, answered on the key signature chart.
bass clef: quick answers
Which line do the two dots mark?
The fourth line from the bottom. The note between the dots is F3, 174.61 Hz.
What are the five lines?
Bottom to top: G2, B2, D3, F3, A3. The saying in the Clef article is “Good Boys Do Fine Always”.
What are the four spaces?
Bottom to top: A2, C3, E3, G3. The same article spells them “All Cows Eat Grass”.
Where is middle C?
One ledger line above the staff. That note is C4, 261.63 Hz.
What did the finder return for the cello prelude?
G major, Camelot 9B, 76% confidence. D major at 6% and G minor at 6% were the next two candidates.
What this page leaves open
- This page is only the bass clef. The treble clef, whose curl wraps G4, is a different staff.
- 174.61 Hz, 196.00 Hz, and the other hertz figures are equal-temperament arithmetic from A4 = 440 Hz. They were not measured off the recording.
- The 76% figure is this 24-second file only. It is not an accuracy rate for every piece written in a bass clef.
- The Anna Magdalena copy prints one sharp after the bass clef. The work list still names the suite G major, and this page does not redraw that signature.
- The recording file is categorized with Bach’s cello suites. Its description does not say which instrument was played, so this page does not add that claim.