6.3 MIDI Editing and Quantization

MIDI editing and quantization are essential skills for music producers. These techniques allow you to fine-tune your digital performances, adjusting everything from timing and velocity to pitch and expression. With the right tools, you can transform a rough MIDI recording into a polished, professional-sounding track.

Quantization is a powerful feature that aligns notes to a rhythmic grid. While it can tighten up sloppy playing, be careful not to overuse it. Finding the right balance between precision and natural feel is key to creating music that sounds both tight and human.

MIDI Editing Basics

Note Manipulation and MIDI Protocol

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• MIDI (Musical Instrument Digital Interface) enables communication and synchronization between electronic musical instruments, computers, and other devices
• Note manipulation adjusts pitch, duration, and placement of individual notes within a MIDI sequence
• Piano roll views in Digital Audio Workstations (DAWs) provide visual representation and manipulation of MIDI data
• Basic editing tasks encompass copying, pasting, transposing, and scaling notes or groups of notes (octave shifts, chord voicing changes)
• Non-destructive editing techniques allow experimentation and easy reversion to original performances (undo/redo functionality, preserving original MIDI data)

Velocity and Controller Adjustments

• Velocity in MIDI corresponds to the force or speed of note playback, typically affecting volume or intensity in virtual instruments
• Velocity editing can enhance dynamic range and expressiveness of MIDI performances (soft pianissimo to loud fortissimo)
• MIDI CC (Continuous Controller) messages modify various parameters of virtual instruments
  • Modulation (vibrato depth)
  • Pitch bend (subtle pitch variations)
  • Expression (overall volume changes)
• CC automation creates evolving, expressive performances (gradual filter sweeps, panning effects)

Quantization for Timing Accuracy

Grid and Groove Quantization

• Quantization aligns MIDI notes to a fixed rhythmic grid, correcting timing inconsistencies
• Grid quantization snaps notes to exact rhythmic divisions (quarter notes, eighth notes, sixteenth notes)
• Groove quantization aligns notes to specific rhythmic patterns or feels (swing, shuffle, humanized grooves)
• Quantization strength determines alignment closeness to the grid
  • 100% results in exact alignment
  • Lower percentages preserve more of the original human feel
• Swing quantization applies rhythmic shuffle to straight rhythms by delaying every other note (50% swing, 66% swing)

Advanced Quantization Techniques

• Iterative quantization gradually moves notes closer to the grid over multiple passes, preserving some natural timing variations
• Quantization can be applied selectively to note starts, note ends, or both
  • Note start quantization for rhythmic accuracy
  • Note end quantization for consistent note lengths
• Over-quantization risks creating robotic-sounding performances, requiring balance between accuracy and original feel
• Combine different quantization methods for optimal results (grid quantization for drums, groove quantization for bass)

MIDI Automation for Dynamics

Real-time and Manual Automation

• MIDI automation records or programs changes in MIDI CC values over time to control virtual instrument parameters
• Real-time automation recording uses hardware controllers (MIDI keyboards, faders, knobs)
• Manual automation involves drawing control data in DAW automation lanes
• Common automated parameters include:
  • Volume (overall level changes)
  • Pan (stereo positioning)
  • Filter cutoff (timbral evolution)
  • Resonance (emphasizing specific frequencies)
  • Effects send levels (varying amount of reverb, delay)

Advanced Automation Techniques

• Envelope generators within virtual instruments can be triggered and modulated via MIDI automation for complex, evolving sounds (ADSR envelopes, LFOs)
• Automation data editing includes scaling and smoothing to refine recorded performances or create precise parameter changes
• Automation curves shape parameter changes:
  • Linear (constant rate of change)
  • Logarithmic (faster initial change, slower towards the end)
  • Exponential (slower initial change, faster towards the end)
• Combine MIDI and audio automation for cohesive, dynamic mixes in production (automated filter sweeps with volume fades)

Troubleshooting MIDI Editing Issues

Timing and Note-Related Problems

• Resolve MIDI timing issues through proper quantization techniques or by adjusting MIDI input latency in DAW settings
• Fix stuck notes (indefinitely playing MIDI notes) by sending MIDI note-off messages or clearing all MIDI data
• Address velocity inconsistencies through:
  • Velocity compression (reducing dynamic range)
  • Normalization (scaling velocities to a consistent range)
  • Manual editing of individual note velocities
• Manage pitch bend and modulation wheel data conflicts by editing or deleting overlapping MIDI CC messages

System and Performance Optimization

• Resolve MIDI channel conflicts by assigning unique channels to each instrument (channels 1-16)
• Identify and remove or edit System Exclusive (SysEx) MIDI messages causing unexpected behavior
• Mitigate MIDI data overload and performance issues by:
  • Optimizing MIDI tracks (removing unnecessary data)
  • Using MIDI plugins efficiently (CPU-friendly virtual instruments)
  • Freezing or bouncing MIDI tracks to audio (reducing real-time processing)