majiayu000 Audio Mixing Skill
The Mix Is Where Magic Happens
This skill handles combining voice, binaural beats, and sound effects into a cohesive, hypnotic audio experience.
Purpose
Mix multiple audio stems at correct levels and apply hypnotic post-processing for production masters.
Standard Stem Levels
CRITICAL: Always use these exact levels.
| Stem | Level | Rationale |
|---|---|---|
| Voice | -6 dB | Reference level, prevents clipping |
| Binaural | -6 dB | Audible but not distracting |
| SFX | 0 dB | Full impact for transitions |
Canonical Mix Command
ffmpeg -y \
-i sessions/{session}/output/voice_enhanced.wav \
-i sessions/{session}/output/binaural_dynamic.wav \
-i sessions/{session}/output/sfx_track.wav \
-filter_complex \
"[0:a]volume=-6dB[voice]; \
[1:a]volume=-6dB[bin]; \
[2:a]volume=0dB[sfx]; \
[voice][bin][sfx]amix=inputs=3:duration=longest:normalize=0[mixed]" \
-map "[mixed]" \
-acodec pcm_s16le \
sessions/{session}/output/session_mixed.wav
Important: Use normalize=0 to prevent unpredictable level changes.
Input Stems
| Stem | File | Required |
|---|---|---|
| Voice | voice_enhanced.wav |
Yes |
| Binaural | binaural_dynamic.wav |
Yes |
| SFX | sfx_track.wav |
Optional |
Never use voice.mp3 - always use the enhanced version.
Hypnotic Post-Processing (MANDATORY)
After mixing, apply psychoacoustic mastering:
python3 scripts/core/hypnotic_post_process.py --session sessions/{session}/
Triple-Layer Hypnotic Presence
| Layer | Enhancement | Level | Effect |
|---|---|---|---|
| 1 | Whisper Overlay | -22 dB | Ethereal presence |
| 2 | Subharmonic | -12 dB | Grounding presence |
| 3 | Double-Voice | -14 dB, 8ms delay | Subliminal presence |
Additional Enhancements
| Enhancement | Description | Default |
|---|---|---|
| Tape Warmth | Analog saturation | 25% drive |
| De-essing | Sibilance reduction | 4-8 kHz |
| Room Tone | Gentle reverb | 4% wet |
| Cuddle Waves | Amplitude modulation | 0.05 Hz, ±1.5 dB |
| Echo | Subtle depth | 180ms, 25% decay |
Output Files
| File | Purpose |
|---|---|
session_mixed.wav |
Pre-master mix (intermediate) |
{session}_MASTER.mp3 |
Final deliverable (320 kbps) |
{session}_MASTER.wav |
Archive master (24-bit) |
Two-Stem Mix (No SFX)
When no SFX track is needed:
ffmpeg -y \
-i sessions/{session}/output/voice_enhanced.wav \
-i sessions/{session}/output/binaural_dynamic.wav \
-filter_complex \
"[0:a]volume=-6dB[voice]; \
[1:a]volume=-6dB[bin]; \
[voice][bin]amix=inputs=2:duration=longest:normalize=0[mixed]" \
-map "[mixed]" \
-acodec pcm_s16le \
sessions/{session}/output/session_mixed.wav
Level Verification
After mixing, check levels:
# Check peak level (should be < 0 dB)
ffmpeg -i session_mixed.wav -af "volumedetect" -f null /dev/null 2>&1 | grep max_volume
# Check LUFS (target: -14 LUFS)
ffmpeg -i session_mixed.wav -af "loudnorm=print_format=json" -f null /dev/null 2>&1
Target Levels
| Metric | Target | Acceptable Range |
|---|---|---|
| Integrated LUFS | -14 LUFS | -16 to -12 LUFS |
| True Peak | -1.5 dBTP | < -1.0 dBTP |
| Peak | -3 dB | < 0 dB |
Binaural Beat Standards
| Brainwave State | Frequency Range | Use For |
|---|---|---|
| Beta | 13-30 Hz | Alert, focused |
| Alpha | 8-12 Hz | Relaxed, light trance |
| Theta | 4-7 Hz | Deep trance, meditation |
| Delta | 0.5-3 Hz | Very deep, sleep-adjacent |
Typical Journey Curve
0:00 - Alpha (10 Hz) - Induction
5:00 - Theta (7 Hz) - Deepening
15:00 - Deep Theta (4 Hz) - Journey core
25:00 - Theta (7 Hz) - Integration
28:00 - Alpha (10 Hz) - Emergence
Troubleshooting
| Issue | Cause | Solution |
|---|---|---|
| Clipping/distortion | Levels too hot | Check stem levels, use -6 dB |
| Binaural inaudible | Level too low | Should be -6 dB (not -12 dB) |
| Voice buried | Binaural too loud | Verify -6 dB on binaural |
| Muddy mix | Sample rate mismatch | All stems same rate (44100 or 48000) |
| SFX too harsh | Level too high | Try -3 dB for gentler SFX |
| Silent output | normalize=1 issue | Use normalize=0 in amix |
Quality Checklist
Before video assembly:
-
{session}_MASTER.mp3exists - No clipping or distortion
- Binaural beats audible but not intrusive
- Voice clear and present
- SFX properly timed (if used)
- LUFS within target range
- Duration matches expected
Integration with Pipeline
Before (dependencies):
- Voice synthesis complete (
voice_enhanced.wav) - Binaural generated (
binaural_dynamic.wav) - SFX track if needed (
sfx_track.wav)
After (next steps):
- Video assembly
- YouTube packaging
Related Resources
- Skill:
tier3-production/voice-synthesis/(input) - Skill:
tier3-production/video-assembly/(next step) - Serena Memory:
audio_production_methodology - Script:
scripts/core/hypnotic_post_process.py