Mixing the montage

Mixing organizes changing relationships between the sounds of a montage.

• establish level and spatial balance
• shape spectrum, dynamics, depth, and focus
• use automation as relationships change through time

Placement, depth, and separation

• panning: positions a sound within the reproduced spatial image
• level and direct-to-reverberant balance: suggest foreground or distance
• spectrum: changes presence, clarity, and apparent depth
• contrast: differences in position, spectrum, and timing help distinguish overlapping sounds

Fusion and separation

Sounds may remain distinct or fuse into a composite event.

Buses, submixes, main output

Reference listening and playback checks

• monitor primarily at a stable, moderate level
• briefly check at quieter and louder levels because perceived spectral balance changes with playback level
• compare reference material at matched loudness
• check the mix on studio monitors, consumer speakers, headphones, and in mono
• take listening breaks and reassess with fresh attention

→ A mix should preserve its essential relationships across playback systems.

Level and loudness measurements

• sample peak (dBFS): highest stored sample value; dBFS means decibels relative to full scale
• true peak (dBTP): estimated maximum of the reconstructed waveform; dBTP means decibels true peak
• RMS (root mean square): average signal level over a defined interval
• LUFS (loudness units relative to full scale): perceptually weighted estimate of program loudness
• LRA (loudness range): statistical measure of loudness variation across a program

Peak, RMS, and crest factor

Two sequences of 1 kHz test signals: sine, square, and pulse train.

▶ Same peak level, different waveforms

▶ Same integrated loudness, different waveforms

→ Equal peak level does not imply equal loudness.

Inter-sample peaks

LUFS, LKFS, and LU

• LUFS (Loudness Units relative to Full Scale): K-weighted loudness referenced to digital full scale
• LKFS (Loudness, K-weighted, relative to Full Scale): numerically equivalent ITU designation
• LU (Loudness Unit): relative loudness difference; 1 LU corresponds to 1 dB

Loudness meter readings

Loudness targets by delivery context

Follow the specification of the broadcaster, platform, institution, or client.

Normalization and level management

• amplification / attenuation: raises or lowers overall level
• peak normalization: sets the highest sample peak to a target
• loudness normalization: adjusts integrated loudness toward a target

→ Normalization changes overall gain, not dynamic range.

Mixing and mastering

Automated mastering services analyze a finished mix and suggest tonal, dynamic, spatial, and level adjustments.

Mixdown, stems, bounce, and consolidation

• mixdown: combine the project through the master bus and render it to one file
• stems: render selected tracks or groups as separate files
• bounce: create new audio from selected material or processing
• consolidate: create continuous files with a common start point

Terminology varies between DAWs.

Final output requirements

Before rendering, define the intended use and technical context: client delivery, platform distribution, art installation, or archive.

• format: file type, sample rate, and bit depth
• channels: mono, stereo, or multichannel
• deliverables: final mix, stems, or both
• level: loudness and true-peak requirements
• documentation: record each file, version, metadata, technical specifications, start time, and duration
• (dither: apply once only when reducing to a lower integer bit depth)

Peak and loudness normalization

Import the supplied test file without track or master processing. Use the same render bounds and WAV format throughout.

1. use Dry run to record the original sample peak, true peak, and integrated LUFS
2. render one version normalized to Peak · −1 dBFS
3. render another to LUFS-I · −16 LUFS, with True Peak limiting · −1 dBTP
4. reimport and measure the original and both renders

Compare their meter readings and perceived loudness. Which target required the larger change, and was limiting applied?

Selected references

• Katz, Bob. Mastering Audio: The Art and the Science. 3rd ed., Focal Press, 2015.
• Brixen, Eddy B. Audio Metering: Measurements, Standards and Practice. Routledge, 2020.
• European Broadcasting Union. EBU R 128: Loudness Normalisation and Permitted Maximum Level of Audio Signals. EBU, 2023.
• International Telecommunication Union. ITU-R BS.1770-5. ITU, 2023.

Related: Fundamentals of Sound · Psychoacoustics · Digital Audio