How to Record Piano — Why Placement Beats Microphone Choice

Piano is acoustically one of the most demanding instruments to record well. The frequency range spans from approximately 27 Hz at the lowest note to over 4 kHz at the highest, with overtones extending well beyond that. The instrument generates sound from strings struck by hammers across a soundboard that is several feet long, inside a case that shapes and reflects the sound before it ever reaches a microphone.

Most engineers approach piano recording as a microphone selection problem. It is primarily a placement problem.

What the piano is doing acoustically

When a key is struck, the hammer hits the string and sets it into vibration. That vibration transfers to the soundboard, which acts as an acoustic amplifier — radiating the sound into the instrument's resonant cavity and outward through the lid. The sound that arrives at a microphone is not just the direct sound from the string. It is the combined result of the string vibration, the soundboard resonance, the internal reflections of the instrument's cavity, and the lid position.

Lid position alone changes what the microphone captures dramatically. A fully open lid radiates sound primarily upward and outward from the open side. A partially open lid changes the internal acoustic environment and the directional characteristics of what exits the instrument. A closed lid transforms the piano into a near-sealed acoustic environment where the soundboard radiation dominates and the high-frequency content is significantly attenuated.

None of these lid positions is wrong. Each produces a different result with different musical applications. What matters is understanding what the lid position is doing and making the choice deliberately.

The spotlighting problem

One of the most common piano recording problems is spotlighting — where notes in certain registers of the piano are louder or tonally different from notes in other registers. Spotlighting is a microphone placement problem, not a microphone quality problem.

When a microphone is positioned close to one end of the piano — the bass strings or the treble strings — the notes closest to the capsule are captured at a different level and with different proximity characteristics than notes further away. The piano does not sound balanced across the keyboard range.

The physics of a microphone's polar pattern determine how this manifests. A cardioid microphone captures on-axis sources more directly than off-axis sources. Positioned inside a piano at close range, the on-axis strings are emphasized relative to the rest of the keyboard. Moving the microphone further from the strings — increasing the distance — reduces the level difference between on-axis and off-axis sources and produces a more balanced capture across the keyboard range.

Understanding the relationship between microphone distance, polar pattern, and the acoustic geometry of the instrument is what allows an engineer to make a placement decision that produces a balanced result before listening to a single take.

Proximity effect inside the instrument

Proximity effect — the bass increase that occurs when a directional microphone is placed close to a source — behaves differently inside a piano than it does in open air. The soundboard and the internal cavity are already producing significant low-frequency energy. Adding proximity effect reinforcement from a close-placed directional microphone can produce a low end that is heavy, uncontrolled, and difficult to EQ into a mix.

The Earthworks PM40 system addresses this by using microphones with no proximity effect regardless of distance — a deliberate engineering decision for the specific acoustic environment of a piano interior. Understanding why that specification matters for this application is part of evaluating any microphone for any specific use.

The placement framework

Before a microphone goes up on a piano, the engineer should have answered these questions: What lid position serves the musical context? Where in the instrument — relative to the strings, the soundboard, and the lid opening — does the polar pattern of the chosen microphone produce balanced coverage across the keyboard range? What is the proximity effect behavior of the microphone at the intended distance, and how does that interact with the low-frequency energy the instrument is already producing?

These questions have engineering answers. They are not answered by choosing the right microphone — they are answered by understanding the relationship between the instrument's acoustic behavior and the physical characteristics of the transducer.

That is the framework Vol 1 of The Studio Edge applies to every microphone placement decision.

Watch: Earthworks PM40 Piano Microphone System Review →

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