Anatomy of a grand piano

A grand piano is about ten mechanisms in one case. Each figure takes one of them apart on a bench and moves it with its real numbers. Start anywhere: hover a part, then click it.

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The part under the pointer, and the figure it opensCase and rim, shaped round the strings236 strings: 20 wound bass notes crossing over the tenorA grand piano 2.11 m long and 1.48 m wide, with its lid taken off. Its 236 strings run from tuning pins in the front of the cast-iron plate, over agraffes or the treble capo bar, across the bridges on the soundboard to hitch pins on the plate's flange: one string per note in the lowest octave, two through the rest of the wound bass, three from F2 up. The bass strings cross over the tenor so their length fits the case, and the longest are still foreshortened to about 1.3 m. Every number in the figure comes from the same scale the detail figures use. Each marker opens the figure for that part: the action (1), the keys (2), the hammers (3), the dampers (4), the pedals (5), the tuning pins (6), the strings (7), the soundboard (8) and the frame (9).
Fig 1Action and escapementOne key's action: the jack throws the hammer free 2 mm before the strings.Fig 2Key balance and touch weightWhy a key goes down at 47 g but only comes back up below 22 g.Fig 3Hammer and voicingFelt that stiffens as it squeezes: contact time and tone against speed.Fig 4Dampers, sustain and sostenutoWhat stops a string, and the two pedals that stop it from stopping.Fig 5Pedals, trapwork and una cordaFrom the foot through the lyre to the keybed, and the shift of the whole action.Fig 6Tuning pin and pinblockOne degree of a pin moves the pitch by almost a third of a semitone.Fig 7String scaleFrom a 2-metre wound bass string to a 5 cm treble wire.Fig 8Bridge and soundboardHow a string's pull becomes a moving board.Fig 9Plate and rimTwenty tonnes of string tension, held by cast iron and laminated maple.