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Audio Processing

Normalisation, trimming, pitch shifting and sample preparation

Overview

EP-PatchStudio includes comprehensive audio processing to prepare samples for the EP-40 Riddim. These processing options apply when using the Batch Processor or exporting from the Sample Editor.

All processing is non-destructive in the editor - changes are only applied when you export or process files.

Channel Conversion

Mono vs Stereo

ModeUse CaseFile Size
MonoMost drums, single-source samples50% smaller
StereoPads, ambiences, stereo-recorded samples2× file size

How It Works

  • Mono conversion: Averages left and right channels into a single centre channel
  • Stereo: Preserves both left and right channels

Recommendation

Use mono for drums and most samples (saves device storage, EP-40 has limited space).

Normalisation

Automatically adjusts audio levels to maximise loudness without clipping.

Settings

  • Enabled/Disabled: Toggle normalisation on/off
  • Headroom: -12dB to 0dB (default: -6dB)

How It Works

  1. Analyses peak level in audio
  2. Scales entire audio to reach target peak level
  3. Preserves dynamic range (proportional scaling)

Headroom Values

  • -12dB: Very conservative, lots of headroom for layering/effects
  • -6dB: Balanced (recommended), safe headroom for device
  • -3dB: Loud, minimal headroom
  • 0dB: Maximum loudness, peaks reach full scale (risk of clipping)

Example

Input: Quiet sample with -18dB peak
Normalise to -6dB headroom
→ Output: +12dB gain applied, peak at -6dB

Recommendation

Use -6dB headroom (standard mastering practice, prevents inter-sample peaks).

Trim Silence

Automatically removes silence from the start and end of samples.

Settings

  • Enabled/Disabled: Toggle silence trimming
  • Threshold: -80dB to -30dB (default: -60dB)

How It Works

  1. Scans from start: finds first sample above threshold
  2. Scans from end: finds last sample above threshold
  3. Trims everything outside these points

Threshold Values

  • -80dB: Very sensitive, keeps quiet room noise/reverb tails
  • -60dB: Balanced (recommended), removes silence but keeps reverb
  • -40dB: Aggressive, removes quiet content and reverb tails
  • -30dB: Very aggressive, may cut wanted audio

Use Cases

  • Recorded samples with pre-roll silence
  • Samples with excessive reverb tails
  • Cleaning up field recordings

Recommendation

Use -60dB for most samples. Disable for samples where you want to preserve room tone or reverb.

Pitch Shift

Transposes audio by semitones without changing duration (time-stretching algorithm).

Settings

  • Range: -24 to +24 semitones (-2 octaves to +2 octaves)
  • Default: 0 (no shift)

Common Uses

  • -12 semitones: Octave down (deeper, darker)
  • -7 semitones: Perfect fifth down
  • -5 semitones: Perfect fourth down
  • +12 semitones: Octave up (brighter, tighter)
  • +7 semitones: Perfect fifth up

How It Works

  • Uses phase vocoder time-stretching algorithm
  • Preserves duration whilst changing pitch
  • May introduce slight artefacts (formant shifting, metallic quality)

Example

Input: Snare drum at C3 (MIDI 48)
Pitch shift: -12 semitones
→ Output: Snare at C2 (MIDI 36), same duration, deeper/fuller

Recommendation

Use sparingly - large shifts (>±12 semitones) can sound unnatural. For subtle tuning, use ±1-3 semitones.

Long Sample Handling (>40 seconds)

The EP-40 Riddim has a 40-second maximum sample duration. When batch processing encounters longer samples, it offers four handling modes:

1. Ask (Default)

Behaviour:

  • Pauses processing and shows modal dialogue
  • User chooses: Split, Pitch Up, Trim, or Skip
  • "Remember choice for this session" checkbox

Use case: When you want manual control over each long sample.

2. Auto-Split

Behaviour:

  • Automatically splits sample into 40-second chunks
  • Naming: filename_00-40s.wav, filename_40-80s.wav, etc.
  • Splits at nearest zero-crossing for click-free transitions

Example:

Input: 100-second pad
→ Output:
- filename_00-40s.wav (0:00-0:40)
- filename_40-80s.wav (0:40-1:20)
- filename_80-100s.wav (1:20-1:40)

Use case: Ambient pads, loops, long textures that can be split without losing musicality.

Pros: Preserves entire audio
Cons: Creates multiple files, may split mid-phrase

3. Pitch Up (+12 semitones)

Behaviour:

  • Pitches sample up by +12 semitones (1 octave)
  • Effect: Doubles playback speed, halves duration
  • Can apply multiple times: +12st → +24st if still too long

Example:

Input: 80-second drone (too long)
→ Pitch up +12 semitones
→ Output: 40-second drone, 1 octave higher

Use case: Drones, pads, loops where higher pitch is musically acceptable.

Pros: Single file, preserves continuity
Cons: Changes pitch/character

4. Trim to 40 Seconds

Behaviour:

  • Keeps first 40 seconds, discards the rest
  • Permanent: Lost audio cannot be recovered

Example:

Input: 100-second sample
→ Output: First 40 seconds only (0:00-0:40)

Use case: When only the intro/start of the sample is needed.

Pros: Simple, single file
Cons: Loses audio data

5. Skip

Behaviour:

  • Skips file entirely (marked as error in queue)
  • Result: File not processed or included in output

Use case: When long samples shouldn't be processed (e.g., full songs, stems).

Workflow Recommendations

ScenarioRecommended ModeNotes
Ambient pads/texturesAuto-SplitPreserves all audio, can layer chunks
Drones/loopsPitch UpMusical if octave up sounds good
Field recordingsTrim to 40sUsually only need beginning
Full tracks/stemsSkipNot suitable for device
Mixed batchAskManual control per file

Processing Order

The batch processor applies settings in this specific order:

  1. Load audio file (decode to AudioBuffer)
  2. Resample (if target sample rate differs from source)
  3. Convert channels (stereo → mono if selected)
  4. Trim silence (if enabled)
  5. Normalise (if enabled)
  6. Pitch shift (if not 0 semitones)
  7. Quantise bit depth (8/10/12/16/24-bit)
  8. Export as WAV (16-bit or 24-bit container)

Important

This order is optimised for quality. For example, normalisation happens after trimming silence (so levels are based on actual audio, not silence).

Related Documentation

Export Options

Learn about sample rates, bit depths and audio format options

View Export Options →

Batch Processor

Process multiple audio files with automated workflows

View Batch Processor Docs →

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