Method and Apparatus for Intelligent Chord Accompaniment

This invention relates to electronic musical instruments, and more particularly to a method and apparatus for providing an intelligent accompaniment in electronic musical instruments.

There are many known ways of providing an accompaniment on an electronic musical instrument. U.S. Pat. No. 4,292,874 issued to Jones et al., discloses an automatic control apparatus for the playing of chords and sequences. The apparatus according to Jones et al. stores all of the rhythm accompaniment patterns which are available for use by the instrument and uses a selection algorithm for always selecting a corresponding chord at a fixed tonal distance to each respective note. Thus, the chord accompaniment is always following the melody or solo notes. An accompaniment that always follows the melody notes in chords of a fixed tonal distance creates a "canned" type of musical performance which is not as pleasurable to the listener as music which has a more varied accompaniment.

Another electronic musical instrument is known from U.S. Pat. No. 4,470,332 issued to Aoki. This known instrument generates a counter melody accompaniment from a predetermined pattern of counter melody chords. This instrument recognizes chords as they are played along with the melody notes and uses these recognised chords in the generation of its counter melody accompaniment. The counter melody approach used is more varied than the one known from Jones et al. mentioned above because the chords selected depend upon a preselected progression of either: up to a highest set root note then down to a lowest set root note etc., or up for a selected number of beats with the root note and its respective accompaniment chord and then down for a selected number of beats with the root note and its respective accompaniment chords. Although this is more varied than the performance of the musical instrument of Jones et al., the performance still has a "canned" sound to it.

Another electronic musical instrument is known from U.S. Pat. No. 4,519,286 issued to Hall et al. This known instrument generates a complex accompaniment according to one of a number of chosen styles including country piano, banjo, and accordion. The style is selected beforehand so the instrument knows which data table to take the accompaniment from. These style variations of the accompaniment exploit the use of delayed accompaniment chords in order to achieve the varied accompaniment. Although the style introduces variety, there is still a one-to-one correlation between the melody note played and the accompaniment chord played in the chosen style. Therefore, to some extent, there is still a "canned" quality to the performance since the accompaniment is still responding to the played keys is a set pattern.

Briefly stated, in accordance with one aspect of the invention, a method is provided for providing a musical performance by an electronic musical instrument including the steps of pre-recording a song having a plurality of sequences each having at least one note therein by transposing the plurality of sequences into the key of C major, and organizing the pre-recorded plurality of transposed sequences into a song data structure for play back by the electronic musical instrument. The song data structure has a header portion, an introductory sequence portion, a normal musical sequence portion, and an ending sequence portion. The musical performance is provided from the pre-recorded data structure by the steps of reading the status information stored in the header portion of the data structure, proceeding to the next in line sequence which then becomes the current sequence, getting the current time command from the current sequence header, and determining if the time to execute the current command has arrived. If the time for the current command has not arrived, the method branches back to the previous step, and if the time for the current command has arrived, the method continues to the next step. Next, the method fetches any event occurring during this current time, and also fetches any control command sequenced during this current time. Determining if the event track is active during this current time, and if it is not active, then returning to the step of fetching the current time command, but if it is active, then continuing to the next step. The next step determines if the current track-resolve flag is active. If it is not active, then the method forwards the pre-recorded note data for direct processing into the corresponding musical note. If, on the other hand, the track-resolve flag is active, then the method selects a resolver specified in the current sequence header, resolves the note event into note data and processes the note data into a corresponding audible note.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is considered to be the invention, it is believed that the description will be better understood when taken in conjunction with the following drawings in which:

FIG. 1 is a block diagram of an embodiment of the electronic musical instrument;

FIG. 2 is a diagram of the data structure of a pre-recorded song;

FIG. 3 illustrates the data structure of a sequence within the pre-recorded song:

FIG. 4 illustrates the data entries within each sequence of a pre-recorded song; and

FIG. 5 is a logic flow diagram illustrating the logic processes followed within each sequence; and

Referring now to FIG. 1, there is illustrated an electronic musical instrument 10. The instrument 10 is of the digital synthesis type as known from U.S. Pat. No. 4,602,545 issued to Starkey which is hereby incorporated by reference. Further, the instrument 10 is related to the instrument described in the inventors' copending patent application, Ser. No. 07/145,094 entitled "Reassignment of Digital Oscillators According to Amplitude" which is commonly assigned to the assignee of the present invention, which is also hereby incorporate by reference.

Digital synthesizers, such as the instrument 10, typically use a central processing unit (CPU) 12 to control the logical steps for carrying out a digital synthesizing process. The CPU 12, such as a 80186 microprocessor manufactured by the Intel Corporation, follows the instructions of a computer program, the relevant portions of which are included in Appendix A of this specification. This program may be stored in a memory 14 such as ROM, RAM, or a combination of both.

In the instrument 10, the memory 14 stores the pre-recorded song data in addition to the other control processes normally associated with digital synthesizers. Each song is pre-processed by transposing the melody and all of the chords in the original song into the key of C-major as it is recorded. By transposing the notes and chords into the key of C-major, a compact, fixed data record format can be used to keep the amount of data storage required for the song low. Further discussion of the pre-recorded song data will be given later.

The electronic musical instrument 10 has a number of tab switches 18 which provide initial settings for tab data records 20 stored in readable and writable memory, such as RAM. Some of the tab switches select the voice of the instrument 10 much like the stops on a pipe organ, and other tab switches select the style in which the music is performed, such as jazz, country, or blues etc. The initial settings of the tab switches 18 are read by the CPU 12 and written into the tab records 20. Since the tab records 20 are written into by the CPU 12 initially, it will be understood that they can also be changed dynamically by the CPU 12 without a change of the tab switches 18, if so instructed. The tab record 20, as will be explained below, is one of the determining factors of what type of musical sound and performance is ultimately provided.

A second determining factor of the type of musical sound and performance is ultimately provided, is the song data structure 24. The song data structure 24 is likewise stored in a readable and writable memory such as RAM. The song data structure 24 is loaded with one of the pre-recorded songs described previously.

Referring now to FIG. 2, the details of the song data structure 24 are illustrated. Each song data structure has a song header file 30 in which initial values, such as the name of the song, and the pointers to each of the sequence files 40, 401 through 40N and 44 are stored. The song header 30 typically starts a song loop by accessing an introductory sequence 40, details of which will be discussed later, and proceeds through each part of the introductory sequence 30 until the end thereof has been reached, at which point that part of the song loop is over and the song header 30 starts the next song loop by accessing the next sequence, in this case normal sequence 401. The usual procedure is to loop through each sequence until the ending sequence has been completed, but the song header 30 may contain control data such as loop control events, which alter the normal progression of sequences based upon all inputs to the instrument 10.

Referring now to FIGS. 3 and 4, the structure of each sequence file 40, 401 through 40N, and 44 is illustrated. Each sequence has a sequence header 46 which contains the initial tab selection data, and initial performance control data such as resolver selection, initial track assignment, muting mask data, and resolving mask data. The data in each sequence 40, 401-40N, and 44; contains the information for at least one measure of the pre-recorded song. Time 1 is the time measured, in integer multiples of one ninety-sixth (1/96) of the beat of the song, for the playing of a first event 50. This event may be a melody note or a combination of notes or a chord (a chord being a combination of notes with a harmonious relationship among the notes). The event could also be a control event, such as data for changing the characteristics of a note, for example, changing its timbral characteristics. Each time interval is counted out and each event is processed (if not changed or inhibited as will be discussed later) until the end of sequence data 56 is reached, at which point the sequence will loop back to the song header 30 (see FIG. 2) to finish the present sequence and prepare to start the next sequence.

Referring back now to FIG. 1, the remaining elements of the instrument 10 will be discussed. The CPU 12 sets performance controls 58 provide one way of controlling the playing back of the pre-recorded song. The performance controls 58 can mute any track in the song data structure 24, as will be explained later. A variable clock supplies signals which provide for the one ninety-sixth divisions of each song beat into the song structure 24 and into each sequence 40, 401-40N, and 44. The variable clock rate may be changed under the control of CPU 12 in a known way.

Thus far, the pre-recorded song and the tab record 20 have provided the inputs for producing music from the instrument 10. A third input is provided by the key board 62. Although it is possible to have the pre-recorded song play back completely automatically, a more interesting performance is produced by having an operator also providing musical inputs in addition to the pre-recorded data. The keyboard 62 can be from any one of a number of known keyboard designs generating note and chord information through switch closures. The keyboard processor turns the switch closures, and openings into new note(s), sustained note(s), and released note(s) digital data. This digital data is passed to a chord recognition device 66. The chord recognition process used in the preferred embodiment of the chord recognition device 66 is given in appendix A. Out of the chord recognition device 66 comes data representing the recognized chords. The chord recognition device 66 is typically a section of RAM operated by a CPU and a control program. There may be more than one chord recognition program in which case each sequence header 40, 401-40N, and 44; has chord recognition select data which selects the program used for that sequence.

The information output of the keyboard processor 64 is also connected to each of the resolvers 701-70R as an input, along with the information output from the chord recognition device 66 and the information output from the song data structure 24. Each resolver represents a type or style of music. The resolver defines what types of harmonies are allowable within chords, and between melody notes and accompanying chords. The resolvers can use Dorian, Aeolian, harmonic, blues or other known chord note selection rules. The resolver program used by the preferred embodiment is given in appendix A.

The resolvers 701-7OR receive inputs from the song data structure 24, which is pre-recorded in the key of C-major; the keyboard processor 64, and the chord recognition device 66. The resolver transposes the notes and chords from the pre-recorded song into the operator selected root note and chord type, both of which are determined by the chord recognition device 66, chord type which is determined by the chord recognition device 66, in order to have automatic accompaniment and automatic fill while still allowing the operator to play the song also. The resolver can also use non-chordal information from the keyboard processor 64, such as passing tones, appogiatura, etc. In this manner, the resolver is the point where the operator input and the pre-recorded song input become inter-active to produce a more interesting, yet more musically correct (according to known music theory) performance. Since there can be a separate resolver assigned to each track, the resolver can use voice leading techniques and limit the note value transposition.

Besides the note and chord information, the resolvers also receive time information from the keyboard processor 64, the chord recognition device 66, and the song data structure 24. This timing will be discussed below in conjunction with FIG. 5.

The output of each resolver is assigned to a digital oscillator assignor 801-80M which then performs the digital synthesis processes described in applicants' copending patent application entitled "Reassignment of Digital Oscillators According to Amplitude" in order to produce, ultimately a musical output from the amplifiers and speakers 92. The combination of a resolver 701-70R, a digital oscillator assignor 801-80M, and the digital oscillators (not shown) form a `track` through which notes and/or chords are processed. The track is initialized by the song data structure 24, and operated by the inputting of time signals, control event signals and note event signals into the respective resolver of each track.

Referring now to FIG. 5, the operation of a track according to a sequence is illustrated. The action at 100 accesses the current time for the next event, which is referenced to the beginning of the sequence, and then the operation follows path 102 to the action at 104. The action at 104 determines if the time to `play` the next event has arrived yet, if it has not the operation loops back along path 106,108 to the action at 100. If the action at 104 determines that the time has arrived to `play` the next event then the operation follows path 110 to the action at 112. The action at 112 accesses the next sequential event from the current sequence and follows path 114 to the action at 116. It should be remembered that the event can either be note data or it can be control data. The remaining discussion considers only the process of playing a musical note since controlling processes by the use of muting masks or by setting flags in general is known. The action at 116 determines if the track for this note event is active (i.e. has it been inhibited by a control signal or event) and if it is not active then it does not process the current event and branches back along path 118,108 to the action at 100. If, however, the action at 116 determines that the event track is active, then the operation follows the path 120 to the action at 122. At 122, a determination is made if the resolver of the active track is active and ready to resolve the note event data. If the resolver is not active the operation follows the path 124,134 to the action at 136, which will be discussed below. If at 122 the resolver is found to be not active, that means that the notes and/or chords do not have to be resolved or transposed and therefore can be played without further processing. If at 122 the resolver track is found to be active, the operation follows the path 126 to the action at 128. The resolver track active determination means that the current event note and/or chord needs to be resolved and/or transposed. The action at 128 selects the resolver which is to be used for resolving and/or transposing the note or chord corresponding to the event. The resolver for each sequence within the pre-recorded song is chosen during play back. After the resolver has been selected at 128, the operation follows path 130 to the action at 132. The action at 132 resolves the events into note numbers which are then applied to the sound file 84 (see FIG. 1) to obtain the digital synthesis information and follows path 134 to the action at 136. The action at 136 which plays the note or chord. In the preferred embodiment, the note or chord is played by connecting the digital synthesis information to at least one digital oscillator assigner 801-80M which then assigns the information to sound generator 90 (see FIG. 1). The operation then follows the path 138,108 to the action at 100 to start the operation for playing the next part of the sequence.

Thus, there has been described a new method and apparatus for providing an intelligent automatic accompaniment in an electronic musical instrument. It is contemplated that other variations and modifications of the method and apparatus of applicants' invention will occur to those skilled in the art. All such variations and modification which fall within the spirit and scope of the appended claims are deemed to be part of the present invention. ##SPC1##