A Modular System Generating Jazz-Style Arrangement for a Given Set of a Melody and Its Chord Name Sequence

Acoust. Sci. & Tech. 29, 1 (2008) #2008 The Acoustical Society of Japan PAPER

A modular system generating Jazz-style arrangement for a given set of a melody and its chord name sequence

Norio Emura1;, Masanobu Miura2;y and Masuzo Yanagida3;z 1Graduate School of Engineering, Doshisha University, Japan 2Faculty of Science and Technology, Ryukoku University, Japan 3Faculty of Engineering, Doshisha University, Japan ( Received 28 February 2007, Accepted for publication 28 August 2007 )

Abstract: There are many music systems available on the market, such as systems for the automatic arrangement of music pieces given as note sequences for solo pianos into a piano score in a speciﬁc style. These systems, however, are usually designed to generate music by concatenation of existing arrangement patterns, so no one can expect that these systems will satisfy user requirements. We propose a system in which a given melody expressed as a note sequence is arranged into a modern Jazz-style score for the piano on the basis of the ‘‘Jazz theory,’’ a theory of harmony used in Jazz and popular music. The performance of the proposed system is evaluated by comparing the results obtained with the proposed system with those obtained using popular arrangement systems available on the market. Experimental results show that arrangement using the proposed system is signiﬁcantly superior to arrangement using systems available on the market.

Keywords: Jazz theory, Chord, Voicing, Piano, Arrangement system

PACS number: 43.75.St [doi:10.1250/ast.29.51]

meet user requirements. In order to improve this situation, 1. INTRODUCTION a new system with a completely new approach to analyzing There are many systems commercially available for input melodies from the viewpoint of functional harmony, automatic music arrangement such as ‘‘Singer Song Writer as well as with additional music theory in case the output Lite 4.0’’ [1], ‘‘Music Builder’’ [2], and ‘‘Band in a box’’ music is expected to be in a particular popular style, must [3]. These systems are usually designed to generate music be developed. Therefore, we implemented the classical by concatenating existing arrangement patterns written by theory of harmony and arrangement techniques described professional musicians in various music genres, but in Jazz theory [4–6] in an integrated modular system. We facilities are limited to a range of prescribed patterns of propose a system in which music is arranged by combi- limited genres and limited arrangement styles. These natorial adoption of modules according to the structure of systems yield almost the same output arrangement to any the input set of the melody and its chord name sequence input melody. Thus, it is impossible for these systems to and user requirements. add individualistic musical ﬂavor or give features charac- 2. STYLE OF MUSIC TREATED teristic to the given music piece. This is because most of those systems arrange music pieces merely by choosing The genre of music called ‘‘Jazz’’ was born in New music fragments from existing arrangement patterns. It is Orleans, the United States, shortly before 1900. People of impossible for those systems to generate new arrangement diﬀerent roots living in New Orleans at that time developed patterns since note allocations do not exist in the built-in Jazz by mixing various kinds of music, such as work songs database. Moreover, in general, these systems are incapable and gospel, with several kinds of traditional music, such of accepting user requirements from the viewpoint of as European music and African music, inducing cultural music theory. Therefore, these systems are not expected to exchanges among them. Jazz was born as a new type of music particular to the local area. Before long, however,

Jazz became music symbolic of the United States. In early e-mail: [email protected] ye-mail: [email protected] 1940, Charlie Parker, a sax player, and his colleagues ze-mail: [email protected] developed a new performance style called ‘‘Be-Bop’’ and

51 Acoust. Sci. & Tech. 29, 1 (2008) introduced various innovative ideas in music by employing new harmonies and new rhythms. Be-Bop is the basis of the so-called ‘‘Modern Jazz,’’ a brand-new style of music that arose in the 1950s. In the 1960s, Jazz performance styles were frequently introduced to various music genres, such as ‘‘Pops’’ and ‘‘Rock,’’ in which harmonies and rhythms characteristic of Jazz were employed. The harmony theory of Jazz that developed based on Be-Bop has been systematized as the contemporary ‘‘Jazz theory.’’ Jazz theory is very important in harmonizing, performing, and Fig. 1 An example of available note scale. analyzing popular music, because numerous Jazz harmonizing techniques have been employed in popular music. C Major 7 Proposed here is an algorithm for arranging popular music based on Jazz theory, assuming that the basis of popular music is Jazz theory, since popular music has long been importing the performance style of Jazz. 3. BASIS OF PROPOSED METHOD Here, the ‘‘Jazz theory’’ is briefly introduced as the basis of the Jazz-style arrangement proposed in this paper. A B C D 3.1. Tension Notes and Available Note Scale The notes forming a chord are called ‘‘chord tones,’’ Fig. 2 Variations of voicing for C Major7. and the notes other than the chord tones are called ‘‘nonchord tones.’’ The most fundamental chords are ‘‘3- note chords’’ or ‘‘triads,’’ consisting of three notes. In Jazz, Voicing techniques are categorized into two types: however, usually ‘‘4-note chords’’ are employed as basic ‘‘Closed (usually called ‘‘close’’) voicing’’ and ‘‘open chords. voicing.’’ Close voicing is a technique of allocating four A note of a melody other than chord tones is notes within an octave. Open voicing, on the other hand, is categorized into two types: ‘‘tension notes’’ and ‘‘approach a technique of allocating four notes spanning more than notes.’’ ‘‘tension notes’’ are defined as notes having either one octave. Figure 2 shows examples of voicing, where 9th, 11th or 13th intervals from the root note, including ‘‘A’’ and ‘‘B’’ are examples of close voicing, and ‘‘C’’ and their substitute variations. A set of tension notes in a single ‘‘D’’ are examples of open voicing. ‘‘D’’ is an example of chord is sometimes called the ‘‘upper structure’’ of the voicing having notes other than chord tones and is called chord, where a chord is a kind of note group consisting of ‘‘tension voicing’’ because the tension notes described notes, usually with 3rd interval accumulation or its octave- above are used. Tension voicing is used particularly when shifted note. An approach note is defined as a nonchord tones having rich color, or ‘‘complex’’ note allocations, are tone that leads to a chord tone via a semitone or a whole required in the piano performance. tone interval. In Jazz theory, various voicing techniques character- An ‘‘available note scale’’ is defined as a scale istic to jazz are described. As fundamental techniques of consisting of chord tones and some nonchord tones. There voicing, ‘‘4-way close voicing’’ and ‘‘drop voicings’’ are can be one or more available note scales associated with a treated here. 4-way close voicing is a technique of single chord. Each available note scale is derived from one allocating four notes within an octave, i.e. a type of close of the church modes employed in church music in voicing. Drop voicing is derived from 4-way close voicing Medieval Europe (see Fig. 1). by moving one or more notes one octave lower. This is a type of open voicing because the interval between the top 3.2. Voicing tone and the bottom tone exceeds one octave. The most ‘‘Voicing’’ means chord assignment including note common drop voicings are ‘‘drop 2’’ and ‘‘drop 3’’ allocation for a given chord name. Although there are wide voicings, where the second or third note from the top note variations of allocating notes by voicing, it is generally (melody note) is dropped one octave. Figure 3 shows performed based on tension notes and an available note examples of 4-way close voicing, drop 2 voicing, and drop scale. 3 voicing for 4 cases of intervals of the melody note,

52 N. EMURA et al.: MODULAR SYSTEM GENERATING JAZZ-STYLE ARRANGEMENT

Fig. 4 Low interval limits.

the lowest limit for each interval (minor 2nd, perfect 5th, etc.) for voicing. The limits are not absolute by rational, but are commonly accepted values regarded as the Fig. 3 Examples of 4-way close voicing, drop 2 voic- maximum acceptable tone height for each interval, as ing, and drop 3 voicing. shown in Fig. 4. The proposed system guarantees the minimum musical aesthetics of the output score by keeping the low interval limit. Table 1 Types of approaches applicable to each voicing.

Voicing Approach type 4. ALGORHYTHM OF JAZZ-STYLE ARRANGEMENT Diminished approach 4-way close Chromatic approach 4.1. Modularization of Voicing Proposed here is an algorithm of jazz-style arrangement Diatonic approach with emphasis on voicing. Several types of voicing Drop 2 Diatonic approach algorithms are modularized and integrated into the system. The system arranges music given as a set of a melody and its chord name sequence by choosing modules according to counting from the root note for 4-note chords. In addition user requirements. to drop 2 and drop 3 voicings, there can be drop 4, drop 2 & 3, drop 2 & 4, drop 3 & 4, and drop 2, 3 & 4 voicings. 4.2. Outline of Proposed Procedure In order to connect neighboring chords smoothly, three Figure 5 shows a flowchart of the proposed system. ‘‘approach types’’ (‘‘approach note voicings’’) are available First, the system analyzes the musical structure of the input in Jazz theory: ‘‘diminished approach,’’ ‘‘chromatic ap- melody and chord sequences specified by the input chord proach,’’ and ‘‘diatonic (scale) approach.’’ Diminished name sequence, and identifies tension notes included in the approach is defined as a voicing technique of allocating chords. Users can choose a note allocation strategy by an approach note to a chord using diminished chords. specifying one of the voicing modules. Our prototype Chromatic approach allocates notes in such a way that each system has only two voicing modules: 4-way close voicing chord tone in the foregoing chord continues to a chord tone and drop 2 voicing. Approach types are regarded as an in the following chord with a chromatic semitone. Diatonic additional process after 4-way close voicing and drop 2 approach is defined as voicing to allocate an approach note voicing, in case a user wants smooth chord transitions. If an to a chord using diatonic chords. In 4-way close voicing, approach procedure is required by a user, the system asks diminished approach, chromatic approach, and diatonic which approach type is desired from among diminished approach can be employed to connect adjacent chords approach, chromatic approach, and diatonic approach after smoothly. In drop 2 voicing, however, diatonic approach is 4-way close voicing. Diatonic approach is employed only exclusively employed in the case of continuing the same after drop 2 voicing. The prototype system, however, can chords. Table 1 shows the types of approaches applicable deal only with diminished approach after 4-way close to each voicing. voicing. At the final stage, the system checks for musical peculiarities of the output score and modifies them if 3.3. Low Interval Limit necessary, referring to the low interval limit criteria. If the If some notes are allocated in a low range, the resultant output score violates any of the low interval limit criteria, sound may cause uncomfortable. In order to avoid this the second lowest note is removed from the chord. situation, Jazz theory constricts the allowable lowest position for each interval. The lowest position for each 4.3. Voicing Modules interval is called the ‘‘low interval limit,’’ and is defined as Figures 6 and 7 show flowcharts of two types for

53 Acoust. Sci. & Tech. 29, 1 (2008)

START Start

Allocate the chord notes in the order of Input melody and note close to the melody note chord name sequence No Is the melody note a chord tone? Input user requirements Yes Delete the closest note to melody note Harmonizing analysis (detect tension notes) Yes Is the chord type 6th? No Allocate M7th note to 2nd voice Voicing modules

. . . No 4-way close Drop 2 †all other Drop †Spread Is the chord type 7th? voicing voicing voicings voicing Yes process process process process What is the degree of a melody note?

No No Other than root, 3rd, Approach type Diatonic approach 7th, #9th, b13th required? required? #9th b13th 3rd, 7th Change root note Change 5th note Change Root or 9th Yes Yes into 9th note into b13th note note into b9th note

Which approach Is the next No type is employed? chord m6th or m7th? process Yes Change 9th note into *A *†B *†C b9th note

process process process . . . Yes Is the previous chord m7th(b5)?

No Change 9th note into b9th note

Yes Violate low interval limits? No * A . . . Diminished approach Last melody note? . . . No * B Chromatic approach Delete the second lowest note Yes * C . . . Diatonic approach No Last chord ? † . . . under construction Yes HALT

Fig. 6 Flowchart of 4-way close voicing. Fig. 5 Outline of the proposed procedure. voicing, 4-way close voicing and drop 2 voicing. Figure 8 sequence) of eight jazz standards was fed into both the shows a flowchart of diminished approach. Drop 2 voicing commercial system and the proposed system, and the is based on 4-way close voicing, and can be regarded as an arrangements output by the two systems are obtained as additional process after 4-way close voicing. MIDI files (SMF). All stimuli are generated by the two systems under the conditions shown in Table 2. In Table 2, 4.4. Resultant Arrangement ‘‘Through harmony’’ in the commercial system represents a Figure 9 shows an example of input information: type of harmonic arrangement corresponding to ‘‘Voicing melody and a chord name sequence. The resultant type’’ in the proposed system. ‘‘Style pick’’ represents a arrangement for the input shown in Fig. 9, obtained with type of rhythmic arrangement. ‘‘ZZJAZZ.STY’’ represents the prototype system using drop 2 voicing, is shown in an orthodox style of swing jazz. The resultant arrangement Fig. 10. yielded by the commercial system is shown in Fig. 11. In order to enable the subjects to distinguish the melody from 5. PERFORMANCE EVALUATION its accompaniment, we use the velocity values ‘‘80’’ for the A perceptual comparison test is conducted between the melody and ‘‘64’’ for the accompaniment. Each output arrangement obtained with the most popular commercial arrangement is played with MIDI sound, and is recorded on system (Band in a box ver. 13) and that obtained with the an audio CD. Stimuli are presented to each subject through proposed system. Eight jazz standards are employed as test stereo headphone speakers using a CD player. Subjects are stimuli. In order to facilitate subjective judgement for the asked to answer the questionnaire shown in Table 3. In the presented stimuli, all stimuli shortened to consist of eight resultant arrangement shown in Fig. 11, the commercial measures. Two listeners with normal hearing are employed system has combined harmonic arrangement and rhythmic as subjects. They teach piano and saxophone at a music arrangement. In order to evaluate the effect of rhythmic academy. Stimuli are prepared by the following proce- arrangement, we asked subjects to evaluate both harmonic dures. Musical information (melody and its chord name and rhythmic aspects holistically.

54 N. EMURA et al.: MODULAR SYSTEM GENERATING JAZZ-STYLE ARRANGEMENT

Start Start

4-way close voicing process 4-way close voicing process

2nd note is dropped one octave Yes Is the melody note a nonchord tone?

3rd note is changed into tension note No

Yes Is the time value an eighth note or less? What is the degree of a melody note? No Other than 11th or #11th Yes Is the melody note anticipation?

11th #11th No No Is the chord type Is the chord type Yes m7th or m6th? M7th or 7th? Is the next chord a diminished chord? No Yes Ye s No

Delete 5th note, and add 3rd note Is the interval between the Yes melody note and the root note of the next chord M2nd or No P4th or M7th? Last melody note? No Yes

No Allocate diminished chord tones Last chord? Yes

Fig. 7 Flowchart of drop 2 voicing. Fig. 8 Flowchart of diminished approach voicing.

Table 4 shows the experimental results. The entries on the left- and right-hand sides, respectively, in each figure pair are the average and the standard deviation of the evaluation score. A t-test shows that the average score of arrangements output by the proposed system are signifi- cantly higher (p < 0:05) than those output by the commercial system for Q1 (Subjects S [tð7Þ¼4:62, p < 0:05] and K [tð7Þ¼2:56, p < 0:05]) and Q2 (Subject S[tð8Þ¼ Fig. 9 Example of input information, melody and its 5:69, p < 0:05]) in Table 4. Although significant differ- chord names. (‘‘All the things you are’’ by Jerome Kern [7]). ences are not recognized between the proposed system and the commercial system for Q2, the average score for the proposed system is slightly better than those for the construction. Moreover, the proposed system can be commercial system. employed as a support system for manual arrangement. These issues will be discussed in the near future. 6. CONCLUSION ACKNOWLEDGEMENTS We proposed a system that employs Jazz theory to yield jazz-style arrangements of a melody given with its This work has been supported by JSPS Research chord name sequence. Experimental results show that the Fellowships for Young Scientists. This work also has been proposed system yields more preferable output than a partly supported by the Academic Frontier Project pro- popular system available on the market. However, the moted by Doshisha University, by the Knowledge Cluster prototype system can deal with only 4-way close voicing Project promoted by MEXT, Japan, by a Grant-in Aid for and drop 2 voicing. Modules for other voicings, such as Scientific Research (No. 16700154), MEXT, and by the other drop voicings, and spread voicing, are under Ryukoku University Science and Technology fund.

55 Acoust. Sci. & Tech. 29, 1 (2008)

Table 2 Conditions of generating arrangement.

System User speciﬁcations Proposed system Voicing type drop 2 voicing Through harmony 4-part drop 2 Commercial system Style pick ZZJAZZ.STY Setting of other parameters Default

Terminology of the commercial system Through harmony: a type of harmonic arrangement Style pick: a type of rhythmic arrangement ZZJAZZ.STY: an orthodox style of swing jazz

Table 3 Instruction and questionnaires. Fig. 10 Arrangement output by the prototype system using drop 2 voicing. Listen to the two arrangements of a musical piece and answer Q1 and Q2 according to your subjective impression.

First, evaluate the more preferable arrangement between the two, using a response score from 1 to 10. Then, comparatively evaluate the other arrangement relative to the score given to the preferred arrangement. Evaluate only the chord sequences. (Eval- Q1 uation of rhythmic arrangement should be neglected.) Comprehensively evaluate to the outputs Q2 including rhythmic aspects.

Table 4 Experimental results.

Q1 Q2 Subjects System A System B System A System B 8.38, 0.74 5.00, 3.71 6.13, 2.13 4.88, 5.27 S [tð7Þ¼4:62, p < 0:05] [tð7Þ¼2:56, p < 0:05] 7.63, 0.84 4.50, 2.00 6.13, 1.55 4.25, 3.93 K [tð7Þ¼5:69, p < 0:05]—

The entries on the left- and right-hand sides, respectively, in each ﬁgure pair are the average and the standard deviation of the evaluation score. Fig. 11 Arrangement output by the commercial system (Band in a box ver. 13).

REFERENCES

[1] Singer Song Writer Lite 4.0, Internet. Co., Ltd. (2004). Norio Emura received B.E. and M.E. degrees [2] Music Builder, Musical Plan. Co. (2004). in Engineering from Doshisha University, [3] Band in a box ver. 13, PG Music. Co. (2004). Japan, in 2002 and 2005, respectively. He is Jazz Study [4] S. Watanabe, (ATN, Inc., Tokyo, 1970). currently a doctoral candidate of the Graduate [5] M. Levine, The Jazz Theory Book (ATN, Inc., Tokyo, 2004). School of Engineering of Doshisha University, [6] T. Pearce and K. Pullig, Modern Jazz Voicings (ATN, Inc., since 2005. In 2007, he became a JSPS Tokyo, Japan, 2002). Research Fellow (DC2). He is a member of [7] S. Ito, The Professional Standard Jazz Handbook (Chuo Art, ASJ and JSMPC. Tokyo, 2004), pp. 10, 12–13, 42, 61, 108, 147, 174.

56 N. EMURA et al.: MODULAR SYSTEM GENERATING JAZZ-STYLE ARRANGEMENT

Masanobu Miura received B.E, M.E. and Masuzo Yanagida graduated from Osaka Ph.D degrees in Engineering from Doshisha University in 1969, and received M.E. degree University, Japan, in 1998, 2000 and 2003 in 1971 and Doctoral degree in 1978, respec- respectively. In 2002, he became a JSPS tively, both from Osaka University, Japan. He Research Fellow (DC2). In 2003, he joined shortly worked with Japan Broadcasting Corpo- Department of Media Informatics, Faculty of ration and returned to Osaka University in 1972 Science & Technology, Ryukoku University as a research associate at the Institute of and is currently an associate professor. He Scientiﬁc and Industrial Research. He was received the Awaya-Kiyoshi Award and the working with ISIR, Osaka University for 9 Sato Paper Award, in 2002 and 2004, respectively. He is a member years from 1978 and moved to Radio Research Laboratory (now, of ASJ, JSMPC, IPSJ, IEICE and JPA. NICT-MIAC after CRL-MPT), Japan, in 1987. He has been working with Doshisha University since 1994. He received the Sato Paper Award from the ASJ in 2004, and Society Award from Information Systems Society of the IEICE, Japan in 2006. Dr. Yanagida is currently Chair of Technical Committee on Musical Acoustics, ASJ, and is a member of ASJ, IEICE, IPSJ, JSAI, JCSS, SOFT, IEEE, and ASA.