| 摘要 |
A device non-integral with the keyboard instrument with which it is used is activated through sheet, card or substitute keyboard means to activate in turn indicating heads mounted over the keyboard of an organ, piano or similar instrument and which designate the keys to be played by lighting or solenoid controlled means. The control sheet or card may utilize raised, indented, or apertured sheets or cards detected through various type contact or photocell means which feed the signal through an electronic relay to the indicating means.
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