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What MIDI velocity really controls
When you play a MIDI keyboard, each note carries a velocity number from 1 to 127. That number records how hard you hit the key. A soft touch might send 30. A firm touch might send 90. A hard strike might send 120. The receiving instrument uses that number to decide how loud and how bright the note sounds. Many sampled instruments change their tone with velocity, not just their volume, so a soft note can sound like a different instrument from a hard note on the same key.
The problem is that hands and keyboards do not always agree. A keyboard with a stiff action may need a hard hit to reach high velocities, so gentle playing sounds too quiet. A light, fast action may jump to maximum velocity too easily, so expressive soft playing is hard. A velocity curve sits between your hands and the instrument and reshapes the numbers: it maps each input velocity to a new output velocity, so the instrument responds the way you want it to.
How to use the shaper
Enter the input velocity you want to test, choose a curve shape, and set the curve strength. The tool shows the mapped output at once, plus a table of mappings for inputs from 0 to 127 in steps of 16, and a graph of the whole curve. Use the table to copy the curve into your keyboard, DAW or plugin, if it accepts a custom curve or a list of values. If your device only offers preset curves, find the preset whose shape best matches the graph you like.
Start with the shape that matches your complaint. If soft playing is too quiet and you want gentle notes to speak more easily, try a logarithmic curve, which lifts low velocities. If your playing jumps to loud too quickly and you want more control at the top, try an exponential curve, which holds low velocities down and reserves the loudest outputs for the hardest hits. If your playing feels fine in the middle but extreme at both ends, try an S-curve, which softens both extremes.
The curve shapes, in plain words
A linear curve changes nothing: input 64 gives output 64. It is the baseline, useful for checking that your keyboard is behaving normally. An exponential curve bends downward in the middle: input 64 might give output 45, so you must play harder to reach loud sounds. A logarithmic curve bends upward: input 64 might give output 85, so soft playing already sounds fairly strong. An S-curve is gentle near both ends and steeper in the middle, which gives fine control for very soft and very loud playing while keeping the middle responsive.
The strength control changes how strong the bend is. A strength of 1 gives a gentle bend. A strength of 5 gives a strong bend, where the middle of the range moves a long way from the linear line. The inverted curve is a special case: it flips the range, so soft becomes loud and loud becomes soft. That is rarely useful for playing, but it is handy for special effects, for example making a quiet pad swell when you lift your hands, or for testing how an instrument responds across its range.
A worked example
Suppose your keyboard feels too sensitive: a normal touch already sends 100, and you cannot play softly. Choose an exponential curve with strength 2. Input 32 now maps to about 15, input 64 to about 45, and input 100 to about 85. Your soft playing now has room to breathe, because the low end of the range stretches out. You must still hit hard to reach 127, but that is the point: the full range of your hand now maps onto the full range of the instrument, instead of bunching at the top.
Now suppose the opposite problem: your keyboard feels heavy, and normal playing only reaches 60, so everything sounds muffled. Choose a logarithmic curve with strength 2. Input 32 now maps to about 55, input 64 to about 85, and input 100 to about 115. Gentle playing now sounds present, and the instrument’s brighter, louder samples finally appear without forcing your hands. In both cases, the fix is not a new keyboard. It is a curve that matches the keyboard you already own to the hands you already have.
Limits to keep in mind
A velocity curve cannot add expression that was never played. If your keyboard only sends a few distinct velocities, or always sends the same value, no curve will create a smooth crescendo. Check first that your keyboard sends a real range: play from very soft to very hard and watch the numbers. If the range is narrow, the problem may be a setting on the keyboard itself, such as a fixed-velocity mode, which a curve cannot fix.
Curves also interact with the instrument. A piano sample library may switch samples at fixed velocity thresholds, for example at 40, 80 and 110. A curve that maps many inputs across a threshold can make the tone jump suddenly, while a curve that keeps inputs on one side of a threshold can hide a sample layer entirely. If a curve sounds uneven, check the instrument’s velocity layers, and aim to spread your playing across them evenly rather than chasing a perfectly smooth mathematical shape.
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