Music – Instruments – Electrical musical tone generation
Reexamination Certificate
1999-10-15
2001-06-12
Nappi, Robert E. (Department: 2837)
Music
Instruments
Electrical musical tone generation
C084S423001, C084S461000
Reexamination Certificate
active
06245985
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a data converter and, more particularly, to a data converter incorporated in a keyboard musical instrument and a method for converting data codes.
DESCRIPTION OF THE RELATED ART
While a pianist is playing a piano, he or she selectively depresses the black/white keys and, thereafter, releases them so as to generate acoustic tones. The depressed black/white key actuates the associated damper mechanism and the associated key action mechanism. The depressed black/white key lifts the damper felt, and the damper felt is spaced from the associated set of strings so as to allow the set of strings to vibrate. On the other hand, the key action mechanism drives the associated hammer for rotation, and the hammer felt strikes the set of strings. Then, the strings vibrate, and generate the acoustic tone. When the pianist releases the depressed black/white key, the black/white key returns toward the rest position. The released black/white key brings the damper felt into contact with the set of strings, again, and damps the vibrations of the set of strings. This results in extinguish of the acoustic tone. If the pianist depresses pedals, i.e., a damper pedal, a sustaining pedal and a soft pedal, the pedal mechanisms impart predetermined effects to the acoustic tones. Thus, the acoustic piano repeats the loop having depressing a black/white key, striking against the strings, releasing the black/white key and damping the vibrations during the performance, and the pedals selectively impart the expressions to the acoustic tones.
An automatic player piano is the acoustic piano equipped with a recording system and a playback system. While a pianist is playing the acoustic piano, each of the black/white keys generates the acoustic tone through the above-described loop, and the pedal mechanisms selectively impart the expressions to the acoustic tones. The recording system monitors the black/white keys so as to generate pieces of music data information representative of the performance. The pieces of music data information are stored in a suitable information storage medium. Otherwise, a tone generator and a sound system produce electronic sounds on the basis of the pieces of music data information in a real time fashion. When the pianist instructs the automatic player piano to reproduce the performance, the playback system reads out the pieces of music data information from the information storage medium, and the actuators selectively actuate the black/white keys and the pedals.
An automatic player piano may be equipped with a silent system. The silent system includes a hammer stopper, which is usually provided between the hammer shanks and the sets of strings. The hammer stopper is changed between a free position and a blocking position. While a pianist is playing a tune on the keyboard, the black/white keys are selectively depressed, and the hammer assemblies escape from the associated jacks. Then, the hammer assembly associated with a depressed key starts a free rotation. The hammer stopper in the free position allows the hammer to strike the set of strings, and the strings vibrate for generating an acoustic tone. However, if the hammer stopper is in the blocking position, the hammer assembly rebounds on the hammer stopper before striking the strings, and any acoustic tone is not generated. A key sensor monitors the associated black/white key, and reports the key motion to a tone generator. The tone generator produces a tone signal, and an electronic sound is reproduced through a headphone.
A shutter plate attached to the associated key and a photo sensor mounted on the key bed form in combination a typical example of the key sensor. However, the prior art key sensor merely detects a couple of points on the trajectory of the associated key, and a data processor calculates the key velocity on the basis of the distance between the detecting points and a lapse of time therebetween.
Another prior art key sensor available for an automatic player piano is disclosed in Japanese Patent Publication of Unexamined Application (laid-open) No. 9-54584. The prior art key sensor continuously detects the key moved on the trajectory, and generates an analog key position signal representative of the current key position on the trajectory.
An opto-electronic sensing device is disclosed in U.S. Pat. No. 5,001339, and the U.S. Patent was assigned to Gulbransen Incorporated. The prior art opto-electronic sensing device is also available for detecting a key motion of an acoustic piano. The opto-electronic sensing device has a flag held in contact with the lower surface of the key at all times, and an opto-electronic sensor monitors the flag so as to generate an output signal indicative of the current position of the flag and, accordingly, the key.
The prior art key sensor disclosed in the Japanese Patent Publication of Unexamined Application supplies the analog key position signal to an analog-to-digital converter, and the analog-to-digital converter converts the analog key position signal to a digital key position signal. The digital key position signal has a bit string of a fixed length. If the potential level of the analog key position signal is too high to be expressed by the fixed-length bit string, the digital key position signal does not accurately represent the current key position due to overflow. On the other hand, if the bit string is too long to express the variation of the potential level, the digital key position signal merely has a low resolution of the current key position due to a narrow dynamic range.
If the digital key position signal has a bit string longer than now, the digital key position signal is prevented from the overflow. However, there remains the low resolution. The analog-to-digital converter is usually connected to a data processor associated with a random access memory. The long fixed-length digital key position signal increases the load of the data processor, and requires the random access memory to have a large data storage capacity. On the other hand, if the digital key position signal has a bit string shorter than now, the resolution is improved. However, the overflow will be frequently takes place, and the digital key position signal is not reliable. Thus, there is a trade-off between the reliability and the resolution.
In order to compromise the trade-off, the manufacturer optimizes the output potential level of the analog key position signal before delivery from the factory. However, aged deterioration is unavoidable. The data processor suffers from a low resolution due to the narrow dynamic range of the digital key position signal.
Moreover, the data processor usually processes a data code in the form of 2
n
. When the bit string of the digital key position signal is expressed in the form of 2
n
, the increase of the bit string results in a characteristic n much longer than now, and the data processor encounters difficulty in the data processing.
SUMMARY OF THE INVENTION
It is therefore an important object of the present invention to provide a data converter, which converts a digital key position signal to a data code to be processed by a data processor at a high resolution without an overflow.
It is also an important object of the present invention to provide a method used in the data converter.
It is also an important object of the present invention to provide a keyboard musical instrument equipped with the data converter.
In accordance with one aspect of the present invention, there is provided a data converter for converting first digital codes represented by a first bit string to second digital codes represented by a second bit string different in the number of component bits from the first bit string, and the data converter comprises a rank assignor analyzing values of the first digital codes generated under reference state and assigning one of ranks representative of different parts of the first bit string to each of the first digital codes depending upon the value under the reference state and an extractor connected to the
Fujiwara Yuji
Sasaki Tsutomu
Ura Tomoyuki
Fletcher Marlon
Morrison & Foerster
Nappi Robert E.
Yamaha Corporation
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