Assertion: harpsichord's stop | /r/HasProperty | unusual
Facets:
value: in the historical period
type: TEMPORAL
Source sentences:
text: Since heavy framing tends to stifle harpsichord sound, instruments were bolstered by other means, notably the addition of a 16' stop (an additional set of strings that played an octave below normal pitch); such stops were somewhat unusual in the historical period but became widespread in the first half of the 20th century.