PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Procedure for arranging backing phrases for ensemble music byevaluating ease of playing on instrumentalists
Nozomiko YASUI1; Masanobu MIURA2
1

Graduate School of Science and Engineering,Saitama University, Japan
2

Kunitachi College of Music, Japan

ABSTRACT
Since arrangement of sheet music for orchestral ensemble requires a certain musical knowledge and expertise,amateur orchestral musicians often have difficulties when they arrange the sheet. An automatic arrangement
method was proposed by employing Eigenmusic which is a set of eigenvector for many music excerpts, inorder to evaluate the similarity among phrases. The difficulty in playing the arranged sheet music, however,
was not evaluated so whether players feel difficulties on playing was out of discussion. This study proposes
procedure for evaluating the degree how easy to play the phrases on sheet music. This procedure generates
phrases for woodwind instruments using a MIDI database of backing phrases. Each musical phrases selectedfrom the database are allocated to instrumentalists. Next, the ease of playing each phrases is evaluated basedon fingering that is important in performance. Finally, phrases evaluated as the easiest are conjoined in each
instrumentalist. We conducted an experiment to investigate the ease of playing for generated sheet music bymusician’s rating. Experimental results showed that the procedure for evaluating ease of playing is effective
so that proposed procedure can generate easier phrases to play than our previous method.
Keywords: Arrangement, backing phrase, ease of playing

1. INTRODUCTION
Orchestral performance involves four instrumental families; string, woodwind, brass, andpercussion. It may contain approximately 50 to 80 instrumentalists. A small number ofinstrumentalists often play together as an ensemble, so they need sheet music appropriate for theirneeds. In order to obtain a sheet music for limited number of instrumentalists, arrangement of a sheetmusic for orchestra is necessary. However, the arrangement requires musical expertise and takes a longtime to complete. Thus, automatic arrangement is preferred to solve this problem.
Several studies of automatic arrangement have been reported, some of which are for arrangement
based on melody extraction or instruments (1) and others are for arrangement of specific sheet musicof wind orchestra into sheet music for a few musicians (2). However, previous studies didn’t focus on
the naturalness of the arranged excerpts. Another method for automatic production of the base part ofpopular music from many MIDI excerpts by using principal component analysis (PCA) (3) wasreported. Abe’s method extracts tracks of the base guitar part from many MIDI excerpts and constructs
a database of the part’s Eigenmusic which is a set of eigenvector for many music excerpts . The
database is used to extract the global average of patterns, which is used to generate the natural patternof the base part.
We proposed a method for automatic arrangement of orchestral performances, employed Abe’s
method in order to take into account the naturalness of arranged sheet music(4). This method arranges
backing phrases. In our previous study, naturalness of music is defined as the extent one can listen
without feeling uncomfortable. We conducted the following steps: i) database construction, ii)
Eigenmusic calculation, iii) automatic arrangement, and iv) performance evaluation. For i), weconstructed a database by using the extracted backing patterns from thousands of MIDI excerpts. Forii), we calculated the Eigenphrase of backing, which is a part of Eigenmusic, where the Eigenphrase ofbacking shows the average backing feature. For iii), we chopped the tracks of the MID IHxcerpts into12

nyasui@mail.saitama-u.ac.jp
miura.masanobu@kunitachi.ac.jp5559

phrases on which we applied a previously proposed method (5) to obtain the phrases. When labelling
the phrases as melody, base, or backing, we used the Eigenphrase of backing. The labelled tracks arethen composed into the arranged sheet music. For iv), we confirmed the naturalness of the arranged
music through an evaluation experiment. Experimental results showed that the proposed method
satisfied the naturalness of the music for listeners. The difficulty in playing the arranged sheet music,
however, was not evaluated so whether players feel difficulties on playing was out of discussion.
Therefore, this study proposes procedure for evaluating the degree how easy to play the phrases
on sheet music. This procedure generates phrases for woodwind instruments using a MIDI databaseof backing phrases.

2. METHOD FOR ARRANGING BACKING PHRASES
The proposed method for arranging backing phrases is outlined in Fig.1. This method was proposed
based on our previous method(4). The procedure for evaluating the ease of playing the phrases on sheetmusic is involved in this study.
First, the tracks of MIDI excerpt inputted in the system are chopped into phrases on which weapplied a previously proposed method. Then, the extent of similarity between those phrases andEigenphrase of backing are calculated to label those phrases as melody, base, or backing. Next, eachmusical phrases labelled as backing are selected phrases that instrumentalist can be played in terms ofpitch and allocated to instrumentalists. The ease of playing each phrases is evaluated based on
fingering that is important in performance. Those phrases evaluated as the easiest are conjoined ineach instrumentalist. Finally, the arranged sheet music is obtained by allocating rests and exchangingphrase.
Backing pattern DB

Eigenphrase ofbacking

Input
MIDI except tobe arranged

Chopping down
into phrase

Calculating the extent ofsimilarity

Labelling phrase to as
melody, base or backing

Instruments
Members
MelodyBacking

Base

Selection of phrases tobe played
Associating instruments
to each track
Evaluating the phrases’
ease of playing
Allocation of rests

OutputArrangement except

Exchanging phrase

Figure 1 – Proposed method for arranging backing phrases

3. FEATURES OF EASE OF PLAYING
We investigated features of ease of playing by questionnaire. 35 instrumentalists were asked toanswer features of phrase that players don’t feel difficulties on playing.
Figure 2 shows the results of questionnaire. As a result, ease of playing depends on range of pitch,
disjunct motion, tempo, key and so forth. Moreover, those features are divided into two categories:
pitch and time. So, we propose procedure for evaluating the ease of playing phrases based on thosecategories.

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13%

㡢ᇦRange

27%

7%

㊴㌍
Disjunct motion䝔䞁䝫Tempo
ㄪྕ
Key13%

㐃➢
Tuplet20%

䛭䛾௚Others

20%

Figure 2 – Result of questionnaire

4. INVESTIGATION OF RHYTHM PATTERN EASY TO PLAY
4.1 Method of investigation of Rhythm Pattern
Specific pitch features of ease of playing were obtained from the questionnaire, whereas specifictime features weren’t clarified. So, we investigated rhythm pattern of ease of playing by anotherquestionnaire. 14 instrumentalists were asked to rate ease of playing on a scale of one to three.
The stimuli were 20 rhythm sheet music obtained from backing pattern DB. 10 of those stimuli
were phrases P i (i:1~10) that occurrence rate is high, the others were phrases Pi (i:11~20) thatoccurrence rate is low. Those phrases were comprised from 2 bars.
4.2 Result of Investigation of Rhythm Pattern
Table 1 shows the result of rating. As can be seen in table 1, it was found that rhythm phrases withhigh occurrence rate are evaluated as easy to play. Figure 3 shows an examples of rhythm sheet music.
We investigated the relation between ease to playing and features of those rhythm. As a result, it was
found that variation in type of note and number of 16th-rest in a phrase affect ease of playing. Figure
4 shows the relation between ease to playing and number of 16th-rest in each phrase. As can be seen inFig. 4, it was found that phrases evaluated as easy to play don’t have 16th -rest. There was a strong
negative correlation with a number of 16th-rest and ease of playing (r = - .83 (n=20)).
Table 1 – Result of investigation of the rhythm pattern
Ease of playing

Phrase ID

Easy

P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P13, P14, P15, P17, P18

Neither

P19

Difficult

P11, P12, P16, P20,(a) Easy to play(b) Difficult to play
Figure 3 – Example of rhythm sheet music

5. PROCEDURE FOR EVALUATING EASE OF PLAYING
As described in chapter 3, pitch features of ease of playing were obtained from the questionnaire.
Moreover, time features of ease of playing were obtained from the investigation as described inchapter 4. In this study, selected backing phrases are evaluated ease of playing depend on thosefeature.

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Number of 16th-rest in a phrase

4P113P12,202P16P191P15 P4,14 P180₇ዌࡋ࡟ࡃ࠸

࡝ࡕࡽ࡛ࡶ࡞࠸

DifficultNeither

P1 P
3,5~10,17P2,13₇ዌࡋࡸࡍ࠸

Easy

Ease of playing
Figure 4 – Result of investigation of the relation
First, over an octave disjunct motion was extracted from each phrase as pitch feature. Specifically,pitch difference pd between two notes in each phrase is calculated as follows.
pd = Hi – Hi-1(1)Here, Hi represents pitch of ith note in each phrase. If the difference pd is not more than an octave,
the phrase is evaluated as easy to play.
Next, similarity between rhythm of those phrases and the rhythm evaluated as easy to play inchapter 4 is calculated. If the similarity score of a phrase is high, the phrase is evaluated as easy to playand selected as a candidate for phrase in arranged sheet music. If the phrase is evaluated as difficult toplay, the phrase is exchanged for other phrases back to selection of phrases to be played. Figure 5
shows an example of the arranged sheet music generated using the proposed p rocedure.

6. EVALUTION EXPERIMENT6.1 Method
We conducted an experiment to investigated the effectiveness of automatically arranged sheetmusic generated using the proposed procedure in terms of instrumentalist impression. We selected 4
sheet music from 5650 MIDI excerpts and arranged those music comprising from 15 to 24 bars byusing the following methods.
z Method B: Arrangement from the previous method (4)z Method P: Arrangement from the method using evaluating ease of playing based on pitchz Method V: Arrangement from the method using evaluating ease of playing based on time valuez Method A: Arrangement from the proposed method in this study
Six players who are playing woodwind instruments participated in our experiment. The players
were asked to play those original and arranged sheet music in random order and then rate theirimpression in terms of naturalness and easiness.
6.2 Results
Figure 6 (a) shows the average and 95% Confidence Interval (CI) of easiness scores, and Figure 6(b) shows the average and 95% CI of naturalness scores. Figure 6 (a) shows that Method A was rated
the highest in all method for easiness. Moreover, it’s found that Method P, V and A were rated higher
than Method B (p < .05). Figure 6 (b) shows that Method B was rated the lowest in all method fornaturalness. In addition, there was no significant difference (p<.05) found among all Methods.

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(a) Original sheet music(b) Arranged sheet music for 3 instrumentalists
Figure 5 – Example of arrangement generated using proposed procedure.
* : p < .05㸪*** : p < .001

***2

**

1
0-1-2-3
BP

3

Average evaluation score

Average evaluation score

3VA

Arrangement methods210-1-2-3BPVA

Arrangement methods(a) Average easiness scores(b) Average naturalness scores
Figure 6 – Results of evaluation experiment5563

7. DISCUSSION
From the results of easiness scores, Method P, V, and A generated sheet music to play more easily
than Method B. So, the analysis of variance (ANOVA) was conducted for the result. This ANOVA
revealed an effect of type of Method (p < .001). To further examining the effect, post hoc analysis
were made using either Tukey’s multiple comparisons test. Tukey’s post hoc analysis showed that
average score of Method A is higher than that of Method B (p < .001). Moreover, it’s shoed that
average score of Method P and V are higher than that of Method B (p < .05). Therefore, the proposed
method is effective for generating sheet music that is easier to play than the method proposed in ourprevious study.
From the results of naturalness scores, Method P, V, and A generated more natural sheet music
than Method B. However, there were no significant difference between each methods. So, we need toinvestigate feature that affect naturalness of music.

8. CONCLUSIONSWe proposed a procedure for arranging backing phrases for ensemble music by evaluating ease ofplaying on instrumentalists. In subjective evaluation experiment of arranged sheet music, we asked
instrumentalists to evaluate arrangement excerpts with our previous method and the proposed method
in terms of naturalness and easiness. Experimental results showed that the procedure for evaluatingease of playing is effective so that proposed procedure can generate easier phrases to play than ourprevious method. Moreover, the proposed method maintained naturalness better than our previous
method. However, no significant difference among those methods was confirmed.
For future work, we will discuss aspects that affect naturalness of music. Moreover, we plan topropose a new arrangement method that can evaluate the ease of playing other instruments, forexample string or brass instrument.

ACKNOWLEDGEMENTS
We express our sincere thanks to Shiori Nabara and the musicians belong to the National Instituteof Technology, Matsue College brass band club for their help.

REFERENCES
1. Shakoh S, Mizuno R, Kitamura, T. Automatic Arrangement System for Ensemble by Assign Melodyand Genarate Accompaniment and Sub-melody. Information Processing Society of Japan. 2010;2010-MUS-85, p. 1-6.
2. Maekawa H, Emura N, Miura M, Yanagida M. On machine arrangement for smaller wind-orchestras
based on scores for standard wind-orchestras. Proc. of ICMPC9, 2006; p. 278-283.
3. Abe Y, Murakami Y, Miura M. Automatic arrangement for the bass guitar part in popular music using
principle component analysis. Acoustical Science and Technology. 2012; 33(4): 229-238.
4. Yamasaki M, Miura M. Use of Eigenmusic to arrange music excerpts. Proc. of ICMPC13, 2014;326-331.
5. Miura M, Inoue Y, Murakami Y, Abe Y. The automatic arrangement system and the method of automaticarrangement. Japan patent JP 2010-017807, January 29, 2010.

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