# `mix mx.fit`
[🔗](https://github.com/mx-music/mx/blob/main/lib/mix/tasks/mx.fit.ex#L1)

Searches for the values of a synth's controls that bring its held notes closest to recordings of them, as `Mx.Fit` describes.

    mix mx.fit clarinet --vel 0.3 BbClar.pp.D3B3.aiff:D3 BbClar.pp.C4B4.aiff:C4 --vel 1 BbClar.ff.D3B3.aiff:D3 --from 160 --control k_odd=-2:2 --control k_att=0.15:x1.15

The synth comes first, then each dynamic as `--vel` and the files played at it, each with the note it starts on, as `mix mx.measure` takes them.
`--control` gives a control the synth takes, its starting value and its step, such as `k_odd=-2:2`; a step written with an x, such as `x1.15`, multiplies and divides instead of adding and subtracting.
`--from` gives the lowest frequency in Hz of the bands compared, all of them below 4 kHz unless given.
It prints how many notes it kept at each dynamic and how many it left out, the score it starts from, each change it keeps, and the best values at the end.
`--drone` measures each file as one note held from its first sample to its last, for a drone plucked again and again, which would otherwise read as a note at each pluck, and leaves out the attack.
`--check` scores the starting values instead of searching, and needs no control; it prints each dynamic's attack difference, and each band's level of harmonics and of noise in the recordings and how far the synth is off, marking those beyond 30 percent or 6 dB.
The recordings' figures are kept in the system's temporary folder and reused until a file changes.

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*Consult [api-reference.md](api-reference.md) for complete listing*