tonal.fm
PRO

All tools offline & ad-free — $9 once

→

A1 · 55.00 Hz

A1 is piano key 13 of 88 and MIDI note 33 - the deep bass register, the territory of bass guitar low strings and organ pedals. Play the pure tone below, tune to it, or explore the note in every octave.

55Hz
Volume50%
Waveform

A1 at a glance

Frequency
55.00 Hz
Wavelength (in air)
6.24 m
MIDI note
33
Piano key
13 / 88
Octave
1
Enharmonic
—

All values assume twelve-tone equal temperament at the international standard pitch of A4 = 440 Hz. In that system every semitone has the same size - a frequency ratio of 2^(1/12) - so A1 is exactly 440 × 2^(-36/12) Hz. Under alternative references the note shifts with the reference: at A4 = 432 Hz, A1 becomes 54.00 Hz.

A in every octave

NoteFrequencyMIDIPiano key
A027.50 Hz211
A1 ←55.00 Hz3313
A2110.00 Hz4525
A3220.00 Hz5737
A4440.00 Hz6949
A5880.00 Hz8161
A61760.0 Hz9373
A73520.0 Hz10585

Each octave doubles the frequency - the simplest relationship in music, and the reason notes an octave apart sound like “the same note, higher”.

Neighboring notes

G1 · 49.00 HzG♯1 · 51.91 HzA1 · 55.00 HzA♯1 · 58.27 HzB1 · 61.74 Hz

One semitone down is G♯1 at 51.91 Hz; one semitone up is A♯1 at 58.27 Hz. Need a frequency between notes, or a different waveform? The tone generator plays anything from 20 Hz to 20 kHz; the note ↔ frequency converter does the math both directions, and the chromatic tuner listens to your instrument and shows the offset in cents.

A1 FAQ

What frequency is A1?

A1 is 55.00 Hz in twelve-tone equal temperament with the standard reference of A4 = 440 Hz. Every semitone step multiplies the frequency by the twelfth root of two (about 1.0595), and A1 sits 36 semitones below A4.

What MIDI number and piano key is A1?

A1 is MIDI note 33 and key 13 of 88 on a standard piano. Octave numbering follows scientific pitch notation, where middle C is C4 (MIDI 60).

How do I tune to A1?

Play the tone above and match your instrument by ear until the beating between the two pitches slows and disappears, or use the chromatic tuner with your microphone for a cents readout. Small mistunings show up as slow beats: one beat per second at this pitch means you are about 31.2 cents off.

Related Tools

Tone Generator

Single tones, 20 Hz - 20 kHz

Signal Generator

Test signals for engineers

Multi-Tone Generator

Several frequencies at once

Sweep Generator

Linear & exponential sweeps

Noise Generator

White, pink & brown noise

White Noise

Full-spectrum masking

Browse all tools →