Velocity Sensitivity and MIDI: Understanding Velocity

Anyone who takes a closer look at the technical specifications or MIDI implementation of an electronic keyboard instrument will sooner or later come across the term “velocity.” But what does speed have to do with playing a keyboard instrument?

In electronic musical instruments, “velocity” does not literally mean speed. Rather, it is the MIDI parameter that represents velocity sensitivity, also known as touch sensitivity. A sensor system detects the mechanical movement of the keys and converts it into digital data to transmit this information to the sound engine. The velocity value, and thus the term, is derived from the speed at which a key is struck.

Velocity in the MIDI System

In the MIDI standard, velocity is transmitted with a resolution of 128 discrete values. This allows touch dynamics to be represented with 128 gradations. In piano sampling, both digital pianos and software instruments use velocity-switched sample layers to realistically reproduce the dynamic sound development of upright pianos, grand pianos, and even electric pianos. Depending on the velocity value, a corresponding dynamic layer is triggered. The better these dynamic layers are matched and balanced, the smoother and more authentic the playing experience becomes.

Velocity vs. Release Velocity

The MIDI protocol also supports release velocity. While it is related to velocity, it measures the speed at which a key is released rather than the speed of the key attack. Release velocity is particularly important for digital pianos, as it allows for nuanced control over the sound’s decay when notes are released. Key-off effects, which are essential for realistic articulation on digital pianos, would not be possible without release velocity.