Recording Acoustic Instruments

Acoustic instruments produce sound through physical vibration of strings, membranes, air columns, or resonant bodies. Capturing these instruments requires understanding how sound radiates from each unique design and selecting microphone approaches that translate that acoustic complexity into recorded audio.

Understanding Acoustic Sound Radiation

Acoustic instruments project sound in complex patterns that vary by frequency and instrument design. A violin radiates differently than a cello, which radiates differently than a double bass, even though all are bowed strings.

Low frequencies typically radiate omnidirectionally, filling the space regardless of instrument orientation. Higher frequencies project more directionally, with specific angles producing brighter or darker tonal balances.

The resonating body of most acoustic instruments contributes significantly to the sound. The guitar’s soundboard, the violin’s belly, the piano’s soundboard all add characteristic color. Capturing the body’s contribution requires appropriate microphone distance to allow the sound to develop.

Microphone Selection Principles

Condenser microphones capture the extended frequency response and transient detail that define acoustic instrument character. Small-diaphragm condensers excel at transient accuracy for plucked and percussive instruments. Large-diaphragm condensers add warmth and body suitable for smoother sources.

Ribbon microphones provide a distinctly different character with rolled-off high frequencies and natural warmth. Stringed instruments often benefit from ribbon’s forgiving nature, which tames the harshness that condensers sometimes capture.

Dynamic microphones see limited use on acoustic instruments due to their reduced sensitivity and rolled-off response. However, in loud situations or for specific tonal effects, dynamics can provide useful results.

Distance and Room Relationship

Microphone distance determines the balance between direct instrument sound and room ambience. Close positioning emphasizes detail and reduces room contribution. Greater distance incorporates more natural reverb and allows complex radiation patterns to blend.

The critical distance, where direct sound and room sound reach equal levels, varies by room. Recording beyond this distance captures more room than instrument. Understanding each room’s critical distance informs positioning decisions.

Room acoustics significantly impact acoustic instrument recording. Reflective spaces add natural ambience that can enhance or overwhelm the direct sound. Dead rooms provide control but may sound sterile. Matching room character to musical intention produces optimal results.

Common Instrument Approaches

Stringed instruments like violin, viola, and cello benefit from microphone positions that capture the complex radiation from body, strings, and f-holes. Positioning above and in front of the instrument at arm’s length provides a natural balance.

Wind instruments project sound primarily from the bell or toneholes. Microphone positions must capture the full range of the instrument rather than focusing only on the bell, which can produce unnatural brightness.

Percussion instruments require attention to attack and body relationship. Close miking captures attack definition while more distant positions allow body resonance to develop naturally.

Stereo Considerations

Many acoustic instruments benefit from stereo capture that presents their spatial character. Piano, harp, and other wide instruments particularly suit stereo microphone techniques.

Coincident stereo techniques provide mono compatibility while capturing width. Spaced techniques create more expansive imaging but introduce phase considerations.

Even smaller instruments can benefit from stereo recording. A violin recorded in a good room with a spaced pair captures spatial dimension impossible with mono recording.

Player and Instrument Variables

Instrument condition affects recording outcomes substantially. Well-maintained instruments with proper setup capture better than neglected ones. New strings on stringed instruments change tonal character significantly.

Player technique contributes as much to the recorded sound as microphone selection. Working with performers to optimize their technique for recording, including dynamics, positioning, and noise control, improves results.

Temperature and humidity affect wooden instruments noticeably. Allowing instruments to acclimate to the recording space before tracking prevents tuning drift and tonal changes during the session.