Instruments and acoustics
Piano action (escapement)
A piano action: the jack lets go just before the string, so nothing is pushing the hammer at impact
This drawing comes from one YAML file. No shape was moved by hand.
Notes in the source (in Japanese)
ハンマーは、最後は誰も押していない。
弦に当たる直前にジャックが外れ(脱進)、ハンマーは自由に飛んで弦を打つ。だから押し続けても弦に押し付けられず、指が決められるのはハンマーの速さだけ。
外れるのは弦の 2〜3mm 手前(レットオフ)。ここが狂うと、音が出ないか二度打ちする。寸法と比は模式。
Source (YAML)
examples/gallery/206-ピアノのアクション.zumen.yaml
More in this field
Guitar frets are a geometric series, and the saddle must still be moved back to play in tune
Hall acoustics: delay is nothing but a difference in path length — one millisecond is 0.34 m
Music engraving: the staff space is the unit for every measurement, and the stem is 3.5 of them
Frets crowd together as you climb because what is divided into twelve is not a distance but a ratio: each semitone multiplies by 2^(1/12), so the twelfth fret lands at exactly half the string and everything beyond it repeats at half size
The black keys are grouped in twos and threes so that a hand can find its place without looking — twelve evenly spaced keys would give no landmark at all — and 88 turns out to be seven octaves plus four: three keys added below and one above
The strings run left to right from high to low and the louder the instrument the further back it sits, so the seating plan is itself a balance control — and "double wind" or "triple wind" names the size of the orchestra by counting only the woodwind
A polar plot of how much a microphone picks up from each direction. The three familiar shapes are not separate inventions but one formula at its ends and middle — omnidirectional, cardioid and figure-of-eight are A = 1, 0.5 and 0 in r = A + (1 - A)cos θ. Solving the same formula gives the dead angles: 180 degrees for a cardioid, 90 and 270 for a figure-of-eight.
The same control means different things depending on where in the chain it sits. An aux send taken before the fader keeps its level when the engineer moves the fader, which is what a performer monitor needs; taken after, it follows the fader, which is what a reverb needs. Insert is in series and cuts the path open; aux is in parallel and branches away and back.