System and method for identifying and converting frequencies on electrical stringed instruments

A method of producing an output from an electrical stringed musical instrument, such as a guitar, having a plurality of strings includes steps of (i) receiving a plurality of analog signals, each analog signal being generated in response to vibration of a corresponding one of the plurality of strings and each analog signal having an associated frequency, (ii) identifying from among the analog signals a particular one of the analog signals having the lowest associated frequency, and (iii) creating an output electrical signal based on only the particular one of the analog signals, the output electrical signal having a converted frequency that is lower than the associated frequency of the particular one of the analog signals.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrical stringed instruments and signal processing circuits therefor, and, more particularly, to a system and method for producing an output from an electrical stringed musical instrument that detects and converts certain frequencies on the electrical stringed musical instrument.

2. Description of the Related Art

Conventional stringed instruments have a limited audio range. For example, the conventional six string guitar has a limited tonal spectrum and is able to achieve sounds above the lowest open string (when tuned at standard “A 440 Hz” the lowest open string, “E”), which vibrates at 82.41 Hz when plucked.

In the case of conventional guitars, while there is typically some overlap in the audio ranges of a lead guitar and a bass guitar, the lead guitar cannot produce the range that the bass guitar can produce. Consequently, it is common for many types of bands or musical groups to include a musician who plays lead guitar, and a second musician who plays bass guitar.

An alternative would be to provide a guitar with the six strings used for a lead guitar, and additional low end strings that would extend the range of the guitar into the range of a bass guitar. This would allow one musician to play bass and lead on the same guitar. However, it would be difficult, if not impossible, for such a guitar to produce the sound that can be produced by conventional lead and bass guitars played by different musicians. This type of guitar would also be extremely difficult to play, due to the presence of more than six independent strings.

Another alternative, represented by U.S. Pat. No. 4,481,854, is to suppress certain frequencies produced by the strings of a lead guitar in an attempt to selectively lower the range of the strings. This does not, however, produce true bass, in that the range of the sound produced by the strings is not actually shifted into a new range.

U.S. Pat. No. 8,502,061 (“the '061 patent”), entitled “Electrical Stringed Instrument and Signal Processing Circuit Therefor” and invented and owned by the inventor of the present application (the disclosure of which is incorporated herein by reference), describes a methodology for extending the range of an electrical stringed musical instrument (e.g., a conventional lead guitar). More specifically, the methodology of the '061 patent employs first and second pickup circuits, wherein the first pickup circuit is associated with a first set of the strings of the instrument (e.g., all of the strings) and the second pickup circuit is associated with only a subset of the strings of the instrument (e.g., the low E and A strings). According to the methodology, the first pickup circuit is structured to produce a first electrical signal corresponding to a first audio range in response to vibration of one or more of the strings in the subset, and similarly the second pickup circuit is structured to produce a second electrical signal corresponding to the first audio range in response to vibration of the one or more of the strings in the subset. However, also according to the methodology, the second electrical signal is converted into a third electrical signal corresponding to a second audio range different than the first audio range (e.g., one octave lower) using a signal processor of the second pickup circuit. As a result, a user of the instrument is able to produce sounds in both the first audio range and the second audio range using the subset of strings, and may do so simultaneously. Thus, in the case where the instrument is a conventional (lead) guitar, the user may generate conventional lead guitar sounds and bass guitar sounds by strumming the subset of strings, and may do so simultaneously.

Furthermore, in the methodology described in the '061 patent, if multiple strings from the subset of strings (e.g., all of the strings in the subset) are played at the same time, the signal from each of those strings will be converted to the lower audio range and multiple bass notes will be resounded. This will often result in an undesirable muddy or muddled sound. This application addresses this issue with a variety of solutions.

SUMMARY OF THE INVENTION

In one embodiment, a method of producing an output from an electrical stringed musical instrument, such as a guitar, having a plurality of strings is provided. The method of this embodiment includes steps of (i) receiving a plurality of analog signals, each analog signal being generated in response to vibration of a corresponding one of the plurality of strings and each analog signal having an associated frequency, (ii) identifying from among the analog signals a particular one of the analog signals having the lowest associated frequency, and (iii) creating an output electrical signal based on only the particular one of the analog signals, the output electrical signal having a converted frequency that is lower than the associated frequency of the particular one of the analog signals.

In another embodiment, an electrical stringed musical instrument is provided that includes a plurality of strings and a pickup circuit structured to (i) generate a plurality of analog signals, each analog signal being generated in response to vibration of a corresponding one of the plurality of strings and each analog signal having an associated frequency, (ii) identify from among the analog signals a particular one of the analog signals having the lowest associated frequency, and (iii) create an output electrical signal based on only the particular one of the analog signals, the output electrical signal having a converted frequency that is lower than the associated frequency of the particular one of the analog signals.

In still another embodiment, a pickup unit for an electrical stringed instrument having a plurality of strings is provided that includes an electromagnetic pickup structured to generate a plurality of analog signals, each analog signal being generated in response to vibration of a corresponding one of the plurality of strings and each analog signal having an associated frequency, and a signal processor structured to (i) identify from among the analog signals a particular one of the analog signals having the lowest associated frequency, and (ii) create an output electrical signal based on only the particular one of the analog signals, the output electrical signal having a converted frequency that is lower than the associated frequency of the particular one of the analog signals.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

As noted elsewhere herein, the '061 patent provides a signal processing circuit that permits any electric stringed instrument to produce audio in an extended range, and an electric stringed instrument that employs the signal processing circuit. However, as also noted elsewhere herein, the system and methodology described in the '061 patent will, in certain circumstances, produce a less than optimal sound. In order to address this issue, the present invention provides an enhancement of the system and methodology of the '061 patent application that prevents muddled bass chords resulting from simultaneous converted frequencies from resounding through an amplifier by giving the lowest analog note (often the “root”) produced by the playing (strumming) of the strings from the subset of strings that is down converted to a lower frequency “priority” and only converting that note/signal to the lower audio range and subsequently outputting it through an amplifier.

For a good understanding of the enhancement of the present invention, it is important to first provide a detailed description of the system and methodology of the '061 patent. Such a detailed description is provided herein in connection withFIGS. 1-11of the present application, which correspond toFIGS. 1-11of the '061 patent. In addition, for ease of illustration, the enhanced methodology of the present invention will be described in detail elsewhere herein in connection with and as implemented on the guitar200and the pick-up unit202shown inFIGS. 9A,9B and10and describe herein. It will be understood, however, that that is meant to be exemplary only and that the enhanced methodology of the present invention may be implemented in connection with other configurations shown in the '061 patent and described herein and/or other similarly configured electrical stringed instruments.

The following is a detailed description of the system and methodology of the '061 patent, wherein exemplary embodiments are described in the context of a lead guitar. While this description describes a guitar constructed according to the teachings of the '061 patent, it also should be noted that the description encompasses a conventional lead guitar that has been retrofitted with the signal processing circuit described herein to achieve a lead guitar with an extended audio range. In the exemplary embodiments, the extended range is the conventional audio range produced by a lead guitar, and at least part of the bass audio range produced by a conventional bass guitar. In the case of both of the exemplary embodiments of the '061 patent described herein, the two lowest strings of the lead guitar are used to produce both the bass component of the extended range, and the lead component. Each of these components can be played alone or simultaneously. The two lowest notes on the lead guitar when tuned to standard tuning of “A 440 Hz” are the low “E” string and the “A” string. When the guitarist chooses to play the lead component, either alone or in combination with the bass component, the amplifier plays the lead sound typically produced by these strings. When plucked, these strings actually vibrate at 82.41 and 110. Hz, respectively. When the bass signal processing circuit is engaged, the frequencies of the electrical signals associated with these two lowest guitar strings are transformed one octave below, producing the exact frequencies found on the low “E” and “A” strings found on a bass guitar. Hence, the bass signal processing circuit, when engaged, converts the frequency of the signal associated with the “E” string to 41.20 HZ, and the signal associated with the “A” string to 55.00 Hz. The bass signal processing circuit permits the audio to be dropped an octave further. In that case, the frequency of the signal associated with the lowest “E” string becomes 20.60 Hz and the signal associated with the “A” string becomes 27.50 Hz. This is an octave below that of a conventional bass when tuned to the standard A=220 Hz pitch. Whether the entire bass range of a conventional bass guitar is produced, or only a part of the range is produced, is a matter of choice. The exemplary embodiments described below use the lowest two strings of the guitar as the source of the bass audio. It is within the scope of the system of the '061 patent to use any or all the strings of a guitar or other stringed instrument as the source of the extended component of the audio. Further, the exemplary embodiments employ the same six strings provided for a conventional lead guitar. Other strings could be used, again, as a matter of choice.

FIG. 1shows a guitar10provided according to the teaching of the '061 patent, along with conventional bass amplifier12and lead guitar amplifier14. Guitar10produces conventional lead guitar audio through guitar amplifier14when strings48of guitar10are played. Guitar10also employs a bass signal processing circuit of the type provided by the '061 patent, the preferred embodiment of which is shown inFIG. 4, to produce sound through bass amplifier12in the bass audio range. In this preferred embodiment, the conventional lead audio and bass audio constitute the extended audio range produced by guitar10. Guitar10can produce lead audio only, bass audio only, or bass and lead audio together.

Guitar amplifier14receives electrical signals from guitar10along line16that are associated with the normal audio range provided by the six strings of guitar10when they are played. Amplifier14produces sound in this range in the conventional manner. A bass amplifier12receives electrical signals from guitar10along a conventional ¼″ instrument cable18that are associated with bass audio produced by the bass signal processor circuit from the two lower strings20and22of guitar10. In the preferred embodiment, as will be seen below, guitar10can produce lead and bass audio simultaneously from strings20and22, or it can produce either lead or bass individually.

Guitar10employs a pair of conventional transducers that produce signals corresponding to the vibration of one or more of the strings48of guitar10. Preferably, the transducers are a pair of conventional electromagnetic pickups32and34that are commonly employed with electric guitars and other stringed instruments. Each of pickups32and34produces in the well-known and conventional manner analog electrical signals related to the frequencies of vibration of the strings proximate the pickup. A first pickup34is associated with all six strings48of guitar10, and produces the electrical signals that are fed to amplifier14to produce the conventional sound produced by a lead electric guitar. A second pickup32is mounted to guitar10below the two lowest strings20and22of guitar10, which is used to convert the vibration of strings20and22to electrical signals that are used to create sound in the bass range.

Referring toFIGS. 1 through 5, guitar10includes bass signal processing circuit36and lead or guitar signal processing circuit38.FIG. 1is partially cut away to reveal a portion of the interior of guitar body42to show internal wiring of guitar10. Lead or guitar processing circuit38(FIG. 5) is the conventional circuit employed in a conventional lead guitar to produce amplified sound from the vibration of the six strings of the guitar. Pickup34is mounted to the upper surface40of guitar body42beneath strings48. Pickup34produces electrical signals along line44to volume control46that are related to the frequencies of vibration of strings48. Volume control46is conventional, and used to control the volume of sound produced through guitar amplifier14. The signals are input from volume control46to tone control50along line52. Tone control50and its conventional circuitry (not shown) are used by the musician playing guitar10to control the tone of the lead audio produced through guitar amplifier14. The signal produced by tone control50is input to output jack54along line56. Conventional ¼″ instrument cable16is plugged into output jack54and guitar amplifier14, along which the output signal from guitar10is input to guitar amplifier14. Guitar amplifier14produces the conventional lead guitar sound produced by a lead electric guitar when its strings48are played.

Bass signal processing circuit36(FIG. 4) is the circuit that allows production of part or all the bass range produced by a conventional bass electric guitar. In the case of the preferred embodiment, the bass range is produced from the lowest two strings20and22of guitar10. Either lead alone can be produced from strings20and22, or bass and lead can be produced simultaneously from strings20and22. Further, lead processing circuit38permits complete suppression of lead from strings20and22using lead volume control46to reduce the lead volume to zero, allowing strings20and22to produce bass sound only through guitar amplifier12.

In particular, pickup32is mounted to the upper surface40of guitar body42beneath strings20and22. Pickup32provides electrical signals along line58to a polyphonic octaver60the frequencies of which are related to the vibrations of strings20and22. Polyphonic octaver60is a conventional, readily available processor that alters the frequencies of the electrical signals it receives using standard algorithms contained and selected by the user on octaver60. A suitable octaver for this purpose is available from Boss/Roland Corporation, as Model No. OC-3 “Super Octave”. In the case of the preferred embodiment, octaver60is used to halve or quarter the frequency of the signals received by octaver60from base pickup32to produce sound in the desired bass range.

Octaver60includes an analog to digital converter, or A/D converter,62, a digital signal processor, or DSP,64, which includes the signal modifying algorithms, and a digital to analog converter, or D/A converter,66. A/D converter62receives the signals produced by bass pickup32along line58. The signals on line58can be substantially the same as the signals on line44in lead signal processor circuit38produced by the vibration of strings20and22. A/D converter62converts the analog signals on line58to digital signals, which are input to DSP64along line68(seeFIG. 5). DSP64converts the frequencies of the signals on line68to the frequencies needed to produce bass audio in the desired range, using standard algorithms in DSP64. DSP64inputs the converted digital signals to D/A converter66along line70. D/A converter66converts the digital signals it receives back to analog signals, which are input to a conventional toggle switch74along line76. Toggle switch74is used either to prevent the signals on line76to be input to bass amplifier12when it is desired not to produce bass audio, or to allow the signals on line76to be input to amplifier12when the production of bass audio is desired. When the guitarist wishes to produce bass only, volume control46can be adjusted to zero to completely eliminate lead audio. When the guitarist wishes to produce lead audio only, toggle switch74is moved to the “off” position to prevent production of bass audio. When switch74is in the “on” position, and volume control46is adjusted to a non-zero position, guitar10produces both bass audio and lead audio. A standard 9 volt battery78provides power to octaver60along lines77and79. Battery78is a conventional alkaline or rechargeable 9 volt battery rated at 300-500 mAh and 9 volts.

Toggle switch74permits the musician to turn the bass audio on and off. When toggle switch74is in the “off” position, bass signal processing circuit36is “open”, signals cannot flow from D/A converter66to output jack72in guitar body42, and strings20and22do not produce bass audio through amplifier12. When toggle switch74is in the “on” position, bass signals can flow from D/A converter66to output jack72. Conventional cable18is plugged into output jack72and bass amplifier12, along which the bass output signals from guitar10are input to bass amplifier12from jack72. Bass amplifier12produces sound from these signals in the desired bass range when strings20and22are played.

A guitar10including a signal processing circuit36can be produced as a new product, or it can result from retrofitting a conventional lead guitar with a bass signal processing circuit36. In either case, as shown inFIG. 1, octaver60can reside in a compartment formed within guitar body42. A panel (not shown) in rear surface82of guitar body42provides access to octaver60, cables76,77and79, and battery78. To retrofit an existing guitar, the necessary interior of body42can be hollowed to form the compartment for octaver60, cables76,77and79and battery78, and bass pickup32, toggle switch74and jack72can be mounted in any conventional manner to body42.

FIGS. 6,6A,6B,7and8show an alternate embodiment100described in the '061 patent. Embodiment100is a guitar that is identical to guitar10, with several exceptions. Components that are common to both guitar10and guitar100are designated by the same reference characters.

Guitar100is identical to guitar10with the exception of the location of the octaver160and the location and physical configuration of the lithium ion or lithium polymer battery178, which are mounted to guitar100in a manner that differs from the mounting of the octaver60and battery78to guitar10. As can be seen best inFIGS. 6,6A,6B and7, a pickup unit102includes a battery178, octaver160and bass pickup132. Pickup132remains a conventional guitar pickup. Battery178is physically configured in any known manner to surround bass pickup132. In this configuration, battery178also functions as the conventional collar employed in a convention pickup to aid in holding the pickup in place on a guitar. Similarly, octaver160is mounted beneath pickup132, between the lower surface200of pickup132and the upper surface142of guitar100. Suitable electrical connections are provided among pickup132, octaver160and battery178in accordance with the teachings provided above. This configuration is simpler, and easier to implement. Battery178features a micro USB port on it, allowing it to be charged by a conventional AC wall charger operating at 110 volts in the US or 220 volts in the UK.

Another variation200includes an all-in-one pickup unit202. Unit202is a modified “humbucker” sized pickup. Unit202takes the place of pickups32and34of guitar10, and includes two pickups204and206. Pickup206acts as the pickup that produces lead audio sound, serving the function of pickup34of guitar10. Pickup204acts as the pickup that produces bass audio from strings208and210. In particular, coils212and214are positioned below strings208and210, and produce electrical signals that are associated with those two strings in the conventional way. Coils216are deactivated, and have no function. A micro USB connection220is formed in pickup ring218of unit202, and is used as a means of charging a battery (not shown) that is mounted within unit202under dummy coils216. An octaver (not shown) is mounted under unit202between the lower surface of unit202and the upper surface222of guitar200. In all other respects, guitar200functions like guitars10and100. Unit202is inserted into a cavity formed in guitar200, just like a conventional “humbucker” sized pickup. The dummy coils or poles216house a battery that powers the DSP unit mounted below or embodied within the guitar200. The pickup ring218around this configuration would feature a micro USB port220, allowing the battery inside the dummy coils216to be recharged when not in use.

Yet another variation,300, achieves the same result. An all-in-one guitar strap system unit302includes a conventional guitar strap304that has been modified to house Octaver DSP unit306, a rechargeable battery308featuring a micro USB charge port, and wires310and312. A floating two piece pole pickup unit318is also provided to produce the signals from strings322and324that are used to produce sound in the bass range. Floating pickup318is a standard, readily available unit that is typically used when it is not desired or not possible to route, drill and/or mount the pickup directly to or within the top surface of a guitar body. In the case of guitar300, however, a floating pickup is used to facilitate providing the signal produced by the “bass pickup” to the electrical components provided in strap304of guitar300.

Unit318includes a pickup316and a mounting317. Pickup316is not mounted directly to the upper surface of guitar body320. Rather, pickup316is secured to clip or mounting317, which in turn is mounted to the side of neck326of guitar300. Thus, mounting317fixes the position of pickup316beneath strings322and324of guitar300. Pickup316itself is a conventional pickup similar in function to the previous versions identified above. However, unit318is what is commonly known in the guitar industry as a “floating pickup”. Rather than being mounted directly to the body320of guitar300, “floating pickup” unit318is mounted to the guitar through a metal clip or mounting317, which is mounted with screws317into the side of the end of neck326of guitar300, as opposed to being mounted into the body320of guitar300. This pickup arrangement allows the entire pickup to “float” above the body320of guitar300but still be located under strings322and324. Unit318functions just like the previously described bass pickups. The benefit of having pickup316located entirely above body320is that all associated wiring is visible and accessible above body320as well. Wiring328coming from pickup316and mounting317is wrapped once around conventional strap lock330on the guitar's body320. Strap304is secured in the conventional manner to strap lock330of guitar body320when in use to mount that end of strap304to body320. Shielded, flexible rubber tubing332surrounds wire310, which is then fed into the top of the guitar strap304. Wire310includes extra slack within the rubber tubing332, allowing the guitar player to move freely while the instrument is in play. The wire310is then connected to the A/D converter of the Octaver306and then out of the D/A converter of the Octaver306. The Octaver306is secured in one place within the strap304by being sewn into place on both sides of its location. Octaver306can be identical to and operate on the signals produced by pickup316in the way as the Octavers in guitars10,100and200. Wire312carries the modified signals produced by pickup316to bass amplifier338.

Wire or cable312travels within strap304to a switch336, which, as with the other embodiments, is used to provide or suppress audio in the bass range. The wire312travels from switch336to the bottom of the strap304where it is soldered to a conventional ¼″ jack334. From the jack334, any conventional ¼″ cable350can be used to connect wiring312to bass amplifier338to produce a bass tone.

Having described the embodiments of the '061 patent, the focus will now turn to a description of the enhancement to the system and methodology of the '061 patent application that is the subject matter of the present invention. As noted elsewhere herein, in the methodology described in the '061 patent, if multiple strings from the subset of strings of the instrument (e.g., all of the strings in the subset) are played at the same time, the signal from each of those strings will be converted to the lower audio range and multiple bass notes will be resounded. Unfortunately, this will in many cases result in less than optimal sound production (e.g., an undesirable muddy or muddled sound). In order to address this issue, described herein is an enhancement of the system and methodology of the '061 patent that prevents muddled bass chords from resounding through an amplifier by giving the lowest analog note (often the “root”) produced by the playing (strumming) of the strings from the subset of strings “priority” and only converting that note/signal to the lower audio range and subsequently outputting it through an amplifier.

As state elsewhere herein, the enhanced methodology of the present invention will, for ease of illustration, be described in detail in connection with and as implemented on the guitar200and the pick-up unit202shown inFIGS. 9A,9B and10. It will be understood, however, that that is meant to be exemplary only and that the enhanced methodology of the present application may be implemented in connection with configurations than as shown inFIGS. 9A,9B and10and/or other similarly configured electrical stringed instruments.

The enhanced methodology of the present invention is described in more detail below in connection with the flow chart ofFIG. 12. However, in general, in the enhanced methodology of the present invention, the digital signal processor (DSP64,FIG. 4) receives an analog signal for each of the strings in the subset of strings associated with pickup unit204that is played (strings208and210) (the “notes in play”), determines which of the notes in play is the lowest frequency, and applies an effect to only that specific string wherein the signal/note is converted to a lower audio range (e.g., down one or two octaves). Thus, with this feature, only the lowest note being played from the subset of strings associated with pickup unit204(i.e., the strings that have the potential for frequency conversion, which are strings208and210in the present example) actually receives the octave effect (as produced by the DSP64of pick-up unit202,FIG. 9A), thereby allowing a conventional electrical guitar to produce a tone in the same range of that found on a bass guitar without a muddy or muddled quality. In other words, when multiple bass frequencies are possible as a result of playing/strumming multiple strings from the subset of strings having conversion potential, the DSP64chooses only the lowest note actually being played/generated (i.e., the lowest note currently being produced by the two strings208and210in the present example) to convert to a different audio range and ultimately send through the output jack to the bass amplifier As described elsewhere herein, this bass output may be provided simultaneously with the conventional lead guitar signals that are generated by strumming the stings of the guitar, including simultaneously with a lead guitar sound generated from the one of the subset of strings associated with pickup unit204and determined to have the low note priority.

Referring toFIG. 12, the enhanced methodology of the present invention according to one exemplary embodiment as implemented in the guitar200and the pick-up unit202shown inFIGS. 9A,9B and10will now be described in more detail. As noted elsewhere herein, this is not meant to be limiting, and it will be understood that that the enhanced methodology of the present invention may be implemented in connection with other configurations shown and described herein and/or other similarly configured electrical stringed instruments. The method begins at step400, wherein the analog signal produced by each of the coils212and214of the bass pick-up unit204in response to vibration of the strings208and210, respectively, is received in the unit including the DSP (e.g., DSP64shown inFIG. 4). Next, at step402, each of the two received analog signals is converted into a corresponding digital signal by, for example, A/D converter62(FIG. 4). The digital signals are then provided to the DSP64. At step404, the DSP64makes a determination as to whether both of the digital signals exceed some predetermined amplitude threshold level. In this exemplary embodiment, this determination is performed in order to make sure that each analog signal was generated in response to an intended force being applied to the corresponding string208,210, as opposed to having been touched accidently when trying to play other ones of the strings. As will be appreciated, such an accidental touching will likely produce a much lower amplitude signal. As will be seen from the description below, in such a case, the analog signal will be ignored in the present exemplary embodiment. This is commonly known as an electronic noisegate, which attenuates signals below the programmed threshold, permitting only those over defined threshold through the signal path for further processing. In addition, when an electric guitar string, such as the lowest string, E, at 0.046″ gauge, is tuned to pitch at 82.41 Hz, it has approximately 17.5 lbs of pressure from the bridge to the nut. Thus, in one non-limiting exemplary embodiment, the predetermined amplitude threshold level may be an amplitude that corresponds to about 0.2 to 0.3 lb/pull (and preferably 0.25 lb/pull) on the string from the pick or finger striking the string.

If the answer at step404is no, meaning that both of the digital signals do not exceed the predetermined amplitude threshold level, then the method proceeds to step406. At step406, the DSP64makes a determination as to whether at least one of the digital signals exceeds the predetermined amplitude threshold level. If the answer is no, then the method ends, as it has been determined that neither analog signal was “intentional.” If, however, the answer at step406is yes, then that means that only one of the two analog signals was “intentional,” and the method proceeds to step408. At step408, the digital signal exceeding the predetermined amplitude threshold level (and only that signal) is converted by the DSP64to a lower frequency/audio range one or two octaves below its current level. The converted (pitch shifted) digital signal is then used to generate an output signal that is provided to the bass amplifier. In the exemplary embodiment, this is done by converting the converted (pitch shifted) digital signal back to analog form using D/A converter66.

If, however, the answer at step404is yes, meaning that both of the digital signals exceed the predetermined amplitude threshold level and are thus “intentional,” then the method proceeds to step410. At step410, the DSP64determines the frequency of each of the analog signals based on the corresponding digital signals generated in step402. Next, at step412, the DSP64determines/identifies which one of the analog signals has the lowest frequency (based on the frequency determinations of step410). Then, at step414, the digital signal representing the lowest frequency analog signal (and only that signal) is converted by the DSP64to a lower frequency/audio range one or two octaves below its current level. The converted (pitch shifted) digital signal is then used to generate an output signal that is provided to the bass amplifier. In the exemplary embodiment, this is done by converting the converted (pitch shifted) digital signal back to analog form using D/A converter66. As will be appreciated, this will result in only one analog signal being pitch sifted and output and will thereby provide a higher quality, non-muddy/non-muddled bass sound.

Thus, in short, in the exemplary embodiment, two separate conventional magnetic pickup coils are used to generate analog signals from the vibration of the corresponding metals strings. These analog signals are then converted to digital signals by a DSP. Then, the DSP detects which digital signal represents the lowest frequency note and only converts that digital signal/note to a lower frequency/audio range (e.g. one or two octave pitch conversion) for output. Thus, when a note is resounded, the system and methodology of the present application attempts to detect the lowest note being played (as effected by any fretting or fingering being done on the strings) by measuring input through separate signals on each string (input generated in the form of analog signals by coils212,214under strings208,210) and only applies the DSP pitch shifting/converting effect to that note which is decidedly the lowest frequency.

As described in detail above, in the illustrated embodiment, the lowest note being played is identified by identifying in the DSP the analog signal having the lowest associated frequency by having the DSP determine the frequency of each of the digital representations of the analog signals. It will be appreciated that this is but one possibility, and that other ways of determine the lowest note being played are also possible.

For example, one alternative way to determine the lowest note being played is by using sensors on or under the fretboard of the instrument (see fretboard280and pressure sensors285inFIG. 13which shows a modified guitar200). More specifically, in the exemplary embodiment, one or more sensors285is/are placed on or under each fret of fretboard280in association with each string208,210. Each sensor is able to detect when finger pressure is being applied to the associated fret and string. The sensors285are coupled to the DSP64, and as a result the DSP64is able to detect/determine which fret and which of the strings208,210is receiving finger pressure. Based on that information, the DSP64may then determine which particular notes are being played on strings208,210as the fretting hand applies pressure to sound notes and, as described elsewhere herein, give priority to the lowest note for the pitch conversion effect.

Another way to determine the lowest note being played is by sending a small electrical signal from one end of the string to the other. On an electric guitar, that would be a 10 millivolt (mV) signal current sent from a micro circuit located under the bridge saddles (see bridge saddles498and micro circuit499inFIG. 13) to the nut of the guitar (see nut496inFIG. 13) along each string208,210. When the finger interrupts the electrical signal being sent from the bridge saddles498to the nut496, a calculation is made in the DSP64to determine where on the string208,210the interruption occurred. Based on that information, the DSP64may then determine which particular notes are being played on strings208,210as the fretting hand applies pressure to sound notes and, as described elsewhere herein, give priority to the lowest note for the pitch conversion effect.

In addition, in a conventionally tuned (standard A 440 Hz) guitar, the lowest open string is tuned to an “E” & vibrates at 82.41 Hz. Any notes at the 5thfret and below on that string (110 Hz and below) can only be produced on that string and cannot be replicated on any other strings of the guitar. Thus, as a further enhancement of the method described herein (e.g.,FIG. 12), in one alternative embodiment, if during processing to determine the lowest note for priority purposes the DSP detects/determines a frequency of 110 Hz or below (which would be food string208in the example), processing to determine the lowest note for priority purposes can stop, as that detected frequency/note will have to be the lowest. That signal can then be immediately given low note priority and the DSP pitch conversion effect can be applied thereto without further processing.

FIG. 14is a schematic diagram of an alternative pick-up unit202′ that may be used in the guitar200ofFIG. 13. Pick-up unit202′ includes a number of switches that may be used to control the operation of guitar200. In particular, pick-up unit202′ includes a main on/off switch500for turning the functionality for extending the range of guitar200as described herein on and off, a selector switch502for determining to what degree the signals will be converted or transformed by the methodology described herein to extend the range of guitar200(e.g., one octave or two octaves), and a selector switch504for turning the low note priority functionality as described herein on and off.