Linear vs Logarithmic MIDI Velocity Curves

MIDI velocity response curves determine how a digital controller translates the physical force or speed of a key strike into a digital value ranging from 0 to 127. While both linear and logarithmic curves bridge the gap between physical touch and sound output, they differ fundamentally in how they scale that force. Understanding the difference between linear and logarithmic velocity curves is essential for optimizing controller playability, matching playing dynamics to specific virtual instruments, and achieving a natural, expressive performance.

Understanding MIDI Velocity

When you press a key on a MIDI keyboard, sensors measure the speed (velocity) of the strike rather than the pressure. This speed is encoded as a MIDI velocity value from 1 (the softest playable note) to 127 (the maximum force).

A velocity curve is a mathematical transfer function that maps the input velocity (how hard you hit the key) to the output velocity sent to your Digital Audio Workstation (DAW) or virtual instrument.

What is a Linear MIDI Velocity Curve?

A linear curve applies a direct 1:1 mathematical relationship between input force and output value. On a graph where the X-axis represents input force and the Y-axis represents output velocity, a linear curve is represented by a straight, 45-degree diagonal line.

• Behavior: Striking the key with 50% physical effort yields an exact output velocity of 64. Double the input force always results in double the output velocity.
• Feel: Predictable, rigid, and uniform.
• Best Used For: Synthesizers, organ patches, step-sequenced parts, and modern electronic production where absolute mathematical consistency is preferred over acoustic realism.

While technically balanced, human hearing and physical muscle control are non-linear. Consequently, playing an acoustic piano plugin with a linear curve often feels stiff, requiring unnatural amounts of force to reach higher velocities or making delicate, quiet passages difficult to control.

What is a Logarithmic MIDI Velocity Curve?

A logarithmic velocity curve applies non-linear scaling to the input force, producing an arched response curve.

In music hardware and software, a logarithmic (or convex) response allows the output velocity to rise more quickly at lighter touches and level off toward the upper limits, or vice-versa depending on whether it is standard or inverse logarithmic.

• Behavior: With a standard logarithmic curve, slight increases in physical effort at the lower end yield noticeable changes in velocity, but higher velocities require significantly more deliberate effort to trigger.
• Perceptual Alignment: Human hearing perceives loudness on a logarithmic scale (measured in decibels), not a linear one. Furthermore, acoustic instruments like grand pianos naturally exhibit non-linear dynamic behavior: striking a key twice as hard does not simply make the sound twice as loud.
• Feel: Expressive, nuanced, and responsive to subtle variations in finger weight.
• Best Used For: Acoustic pianos, orchestral instruments, dynamic drum kits, and players with a lighter touch who want greater control over low-to-mid dynamics without accidentally triggering harsh, maximum-velocity samples.

Key Differences at a Glance

• Mathematical Mapping: Linear mapping increases at a constant, fixed rate. Logarithmic mapping changes at a variable rate based on mathematical exponents.
• Dynamic Nuance: Logarithmic curves provide greater resolution in the lower-to-middle dynamic ranges (pianissimo to mezzo-forte), making nuanced performances easier to execute. Linear curves distribute resolution evenly across all ranges.
• Playability: A linear curve treats a keyboard like a digital trigger mechanism. A logarithmic curve behaves more like an acoustic mechanism, compensating for human physiology and hearing perception.

Selecting between linear and logarithmic velocity curves ultimately depends on your playing style, the weighted action of your MIDI controller, and the type of instrument you are controlling.