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Title

iDAF‑drum: Supporting Everyday Practice of Drumby Adding an Unperceivable Factor

Author(s)Nishimoto, Kazushi; Ikenoue, Akari; Unoki,
MasashiCitation

Proceedings of 9th International Conference on
Knowledge, Information and Creativity Support
Systems: 384‑395

Issue Date

2014

Type

Conference Paper

Text version

author

URL

http://hdl.handle.net/10119/14745

RightsKazushi Nishimoto, Akari Ikenoue and Masashi
Unoki, Proceedings of 9th International
Conference on Knowledge, Information andCreativity Support Systems, 2014, pp.384‑395.
http://kicss2014.cs.ucy.ac.cy/index.php

Description

Japan Advanced Institute of Science and Technology

iDAF-drum: Supporting Everyday Practice ofDrum by Adding an Unperceivable Factor
Kazushi Nishimoto, Akari Ikenoue ⋆ , and Masashi Unoki
Japan Advanced Institute of Science and Technology
knishi@jaist.ac.jp,identity0811@yahoo.co.jp,unoki@jaist.ac.jp
http://www.jaist.ac.jp/ks/labs/knishi/

Abstract. To achieve excellent drum performances, suﬃcient use of theextensor muscles of the wrists is important. However, it is actually very
diﬃcult and there have been no eﬃcient methods and tools to train
them. This paper proposes iDAF-drum, which is a novel training system of the extensor muscles in everyday drum practice. “iDAF” is anacronym of “insigniﬁcantly delayed auditory feedback” and usual people
cannot perceive such a very slight delay. We found an interesting phenomenon that drummers raise the drumsticks higher than usual by inserting the unperceivable delay between impact and sound. By exploiting
this phenomenon, iDAF-drum can eﬃciently train the drummers’ extensor muscles without giving them any unusual feeling. We demonstrate
the eﬃciency of iDAF-drum based on user studies and discuss possibilities of exploiting unperceivable factors like iDAF for eﬀectively bringing
out and fostering buried creative abilities.
Keywords: Unperceivable factors, drum practice, delayed auditory feedback, illusory feelings.

1

Introduction

Good control of drumsticks is very important in drum performance. A drummer
must not only drum at accurate tempo with adequate strength but also control
the tone of the drum through the motion of the sticks. Wrist motion is the key
to stick control. The ﬂexor muscle, which contracts to cock the wrist, and theextensor muscle, which contracts to extend the wrist, govern the wrists’ motion.
Balanced usage of both muscles allows the drummer to drum fast for a long
period as well as to improve the tone of the drum[1–4].
However, it is generally diﬃcult to master the technique of stick control where
the extensor muscle is suﬃciently used. Special heavy sticks have often been used
for practicing the intentional use of the extensor muscle in traditional drum
training methods. However, using such heavy sticks causes damage to wrists due
to overload. A new method for training the dominant use of the extensor muscle
has recently been developed [5]. In this method, a special drumming form that⋆

Currently with Next Co., Ltd.

2iDAF-drum: Supporting Everyday Practice of Drum

forces the drummer to use the extensor muscle is proposed. However, this form
is quite diﬀerent from normal ones. The drummer has to master the special
form only for training the extensor muscle. Thus, this method is not so eﬃcientbecause it requires extra training time.
This paper proposes a novel method exploiting an “insigniﬁcantly delayed
auditory feedback (iDAF)” for training drum stick control and a support systemfor drumming practice named iDAF-drum [6]. Here, insigniﬁcantly delayed auditory feedback means a very short time delay between the impact of the stick withthe drumhead and the emission of sound. Typically, humans cannot recognize
the existence of iDAF: iDAF is unperceivable. Diﬀerent from the conventional
methods, drummers will not ﬁnd any diﬀerence between drumming under our
method and the conventional one. Nonetheless, it allows drummers to eﬃciently
train in a way where the extensor muscle is suﬃciently used.

2

Related Works

Several support and augmenting systems for drum performance have been studied so far. Jam-O-Drum [7] is a collaborative multimedia percussion system for
performing interactive improvisations. Voice Drummer [8] is a system for inputting a percussion score by so-called “voice percussion.” Many such systems
focusing on drumming performance have been proposed, created and studied.
However, they did not support practice while training how to use the extensor
muscle of the wrists.
In contrast to performance training, there have not been so many attempts
to support practice of the drum. Iwami and Miura [9] studied a computer system
to help drummers practice loop patterns of the drum. It visualizes situations ofdrumming such as ﬂuctuation of timing and impact strength to allow drummers
to self-check their performances. This system shows where mistakes are made,but it does not tell the drummer how to practice to correct them. Beatback[10] is a system for supporting rhythm practice. However, “practice” here means“exploration” or “creation” of novel rhythmic patterns. The system encourages
such generating processes of rhythm by working as a virtual partner of musicalperformance. Thus, this system does not truly focus on correction of the wrong
drumming form.
Tsuji and Nishitaka [11] developed a system to improve drumming form. By
showing rhythm lapses, drum-form lapses, hand-stroke amplitude, and striking
strength, it leads the drummer to correcting his/her wrong form. This objectiveof that study is quite similar to ours. However, the way to correct the wrong
form is indirect: No concrete instructions are provided. In contrast, we attempt
to directly correct wrong usage of the muscles.
Several patents to improve drumming form have been applied for. “Practiceaid device for percussionists” [12] proposed a small spacer for correcting the wayof holding the drumsticks. “Muscle control development system and kit therefor”[13] proposed drum pads made of elastic materials. By preparing multiple pads
whose degree of rebounding are diﬀerent and by drumming on those pads, users

iDAF-drum: Supporting Everyday Practice of Drum3

can train in ways of stick control while hitting drums having diﬀerent rebounding
features. They aimed at improving drumming form, but they did not focus on
training the extensor muscle.
“Drummer stick control up-stroke practice method and device” [14] proposeda special attachment that is mounted over a drumhead: A horizontal bar is set
tens of centimeters above the drumhead. By intentionally hitting the bar by the
up-stroke of the sticks just after hitting the drumhead, users can learn ways tointentionally raise the sticks after impact. The objective of this patent is similar
to ours: It focuses on the up-stroke that requires the drummer to use the extensor
muscle. However, it also imposes special and unusual ways of performance on
the drummer. There is the risk of he/she adopting the bad habit of excessively
raising the sticks.
Consequently, although various systems for supporting the practice of drumming performance have been proposed, created and studied, no system has focused on training the extensor muscle. Furthermore, there has been no attempt
to exploit the eﬀects of unperceivable factors like iDAF.

3

Proposed Method and System

3.1

Definition of iDAF and Method

Delayed auditory feedback (DAF) usually means a feedback of voice to its
speaker with a 100∼200 msec delay. It is well known that such a DAF prevents the speaker from smoothly speaking, since it leads to the phenomena of
repeating syllables and stuttering [15].
If a DAF is applied to the performance of a musical instrument, behaviors
in the performance change. In the case where a person repeatedly taps using
his/her foreﬁnger, the raising height of the foreﬁnger tends to increase if thetapping sounds are delayed [16]. Therefore, by applying this result to drumming,
we can expect that the raising height of the drumsticks will increase and that
this will in turn provoke a motion that makes much greater use of the extensor
muscle. However, such a large delay as 100∼200 msec makes it diﬃcult for people
to play musical instruments, and they became unable to keep accurate rhythm[17]. As a result, it becomes practically impossible to practice drumming.
Insigniﬁcantly delayed auditory feedback (iDAF) is an auditory feedback witha very short delay that people normally cannot perceive. It is known that people
can usually perceive a time lag between an event and its sound if it is longer than
20∼30 msec [18, 19]. Therefore, we deﬁne iDAF, in this paper, as an auditory
feedback with a delay not exceeding 30 msec.
We propose a novel method for drumming practice that exploits iDAF. It
provides an unperceivable delay between the impact of the stick and the soundemission from the impact. If it can change a drummer’s motion similar to the
behavior change of the foreﬁnger tapping with a long delay [16], the extensor
muscle would come to be used much more without obstructing the drumming.

4iDAF-drum: Supporting Everyday Practice of Drum

Fig. 1. System setup of iDAF drum

3.2

System Setup

Figure 1 illustrates the system setup of iDAF-drum. iDAF-drum consists of anelectrical drum pad (YAMAHA TPS80S), a trigger module (YAMAHA DTXPRESS), a MIDI sound module (Roland SD-50), a USB-MIDI interface (YAMAHA
UX-16), and a Windows PC (Windows VISTA). An impact signal from the electrical drum pad is input to the trigger module and then converted to a MIDI
signal. The MIDI signal is input to the Windows PC. After a given time (shorter
than 30 msec) passes, the PC inputs the signal into the MIDI sound module.
Finally, a hitting sound is emitted with an insigniﬁcant delay.
For convenience of data analysis, when the Windows PC receives the MIDI
signal from the trigger module, the PC outputs a pulse signal from its serial
port that is used for synchronizing with the myoelectric potential data of theextensor muscles (we call this pulse signal “synchronization signal” hereafter).
We implemented the software runs on the PC for adding the delay while using
C♯. In order to achieve 1-msec-order resolution for adding the delay, we used theWindows API functions. All of the sounds of the performance and a metronome
are output from a headphone. We assigned a snare drum tone as the performancesound.

4

Estimating Eﬀects of iDAF on Drumming

To the best of the authors’ knowledge, there has been no study on estimating
the eﬀects of such a very slightly delayed auditory feedback as iDAF. Therefore,
this section investigates the eﬀects of iDAF on drumming performance. First, we
conﬁrm that iDAF produces no negative eﬀects, and then we investigate whether
iDAF changes the drumming behavior so that the drummer begins to use theextensor muscle to a much greater extent.
4.1

Experimental Procedure

We employed 12 subjects (Sex: 7 males and 5 females; Age: Average 20.67 y/o,
STDV 3.94; Drum experience: Average 5.78 years, STDV 3.67, Max 13.0 years,

iDAF-drum: Supporting Everyday Practice of Drum5

Min 0.5 years). We asked them to hit the electrical drum pad using sticks heldby the right and left hands alternatively along with a metronome sound thatticks every 250 msec. We instructed them to hold the sticks in a matched-grip
manner.
Before starting experimental drum performances, we measured the maximum voluntary contraction (MVC) of the radial extensor muscle of the wrist
three times for each of the subjects. In the experiment, we asked each subject toconduct four performance sessions whose delay times changed in the order of 0,
20, 10 and 30 msec. The subjects were asked to perform for 90 sec in each session. How they synchronized with the metronome was individually diﬀerent, e.g.,some subjects attempted to set the timing of sound emission to the metronome
sound while others attempted to set the timing of impact to the metronome.
Therefore, to standardize the way of synchronization, we asked the subjects towear an eye mask and to attempt to set the timing of the sound emission to
the metronome as much as possible. No warm-up was permitted. During eachsession, the myoelectric potential data of the extensor musclewere measured using electromyography (TEAC Polymate AP1532). In addition, we recorded theperformances using a high-speed video camera. After ﬁnishing each session, we
asked the subject whether he/she felt or found anything unusual.
To increase the signal-to-noise ratio of the myoelectric potential data between the synchronization signal and 250 msec before that, we applied a signalaveraging method to the obtained data, and the root mean square (RMS) of thecleaned data was calculated. Then, the data were normalized using the MVC ofeach muscle so that the MVC value was set to 100 percent.
4.2

Results

The ANOVA for average IOI values of all subjects showed no signiﬁcant maineﬀect with or without delay (F (3, 44) = 0.4, p < 0.754). In the previous studies on DAF with 100∼200 msec delay, an expansive speaking phenomenon wasobserved. However, such an expansive phenomenon does not arise under theiDAF condition. We also calculated the coeﬃcient of variation (CV), which isusually used as an indicator of confusion caused by DAF. As a result, we could
not ﬁnd any signiﬁcant diﬀerence between with and without insigniﬁcant delay(F (3, 44) = 0.436, p < 0.728). From these results, we can conclude that iDAF
does not at all cause the confusion that arises in DAF. From the inquiry results
obtained after each session, only one subject reported that he felt a slightly
strange feeling when delay was given. However, he did not become unable toperform drumming and he could play as usual. None of the other subjects felt
any diﬀerence or strangeness.
Figure 2 shows snapshots taken with the high-speed camera at one minutefrom the beginning of each session. The small red circle in each picture shows
the head of the stick. The upper row shows the top reach point of the stick heldby the right hand and the lower row shows that of the left hand. The delay times
were 0, 10, 20 and 30 msec from the leftmost to the rightmost pictures. It can

6iDAF-drum: Supporting Everyday Practice of Drum

Fig. 2. Top reach points of the stick for 4 delay times. Upper row: Right hand, Lower
row: Left handbe seen that the more the delay time increases, the higher the stick is raised.
This tendency was observed for most of the subjects.
Figures 3 and 4 show average electromyograms (EMGs) of the extensor muscle of the left and right wrists, respectively, for each delay time. The verticalline drawn at 250 msec shows the impact timing. Figure 3 shows that the peakvalue of EMG with no delay (blue line) is smaller than the other peak values
with delays. In particular, the peak value with 10 msec delay (broken red line)
is about 0.6% larger than that with no delay. In contrast, Figure 4 shows thatthe peak value of EMG with no delay is larger than those with delays. We calculated gross value of EMG for each delay and compared the gross value with nodelay to the gross value with each delay by the t-test. As a result, the diﬀerence
between the gross value with 10 msec delay and that with no delay for the left
hand is marginally signiﬁcant (t(11) = 1.892, p < 0.085). However, no signiﬁcantdiﬀerence could be found in all other combinations. As shown in Figure 2, thesubjects raised the sticks higher under the iDAF conditions. Although this suggests that they used the extensor muscle much more, it was not supported by
the electromyograms.
4.3

Discussion

From the results shown in Figure 2 and responses to inquiries after each session,
we obtained very interesting ﬁndings: The motions of drumming performancechanged due to iDAF and the subjects tended to raise the sticks much higher
than usual (with no delay), although they were not aware of the delays. Thissuggests that iDAF can successfully induce the performer to suﬃciently use
the extensor muscle in drumming performance without perceiving diﬀerences.
It remains unrevealed why humans react to such unperceivable auditory delays.
This is a very interesting research issue, but it is out of the scope of this paper;

iDAF-drum: Supporting Everyday Practice of Drum

7

Fig. 3. Electromyograms of extensor muscle of left hand for each delay time

Fig. 4. Electromyograms of extensor muscle of right hand for each delay time

the objective of this paper is to create a useful support system for practicing
drum performance. We only apply this phenomenon to the support system inthis paper; elucidating its mechanism remains a future work.
Although iDAF may be able to provoke dominant use of the extensor muscle,
the results shown in Figures 3 and 4 do not support the idea that the subjects
came to use the extensor muscle more than usual when iDAF was given. Rather,although no signiﬁcance was obtained, the longer the delays were, the less theextensor muscle was used for the right hand. For the left hand, the extensor
muscle was mostly used with 10 msec delay, and then the longer the delays
became, the less the extensor muscle was used.
It can be assumed that the reason why the sticks were raised higher when the
delays were given is that the subjects unconsciously control the impact timing.
However, to do so, they probably use not only their wrists but also their elbows.
It becomes impossible to eﬀectively make subjects use their wrist extensor
muscle if their elbows move. A possible method of making their elbows not
move is to immobilize their upper arms. However, such a method imposes too
great a load on the extensor muscle, and it can damage the extensor muscle ina similar way to the method using heavy sticks. Therefore, we think a bettermethod is to make the impact-impact interval so short (namely, to make playfaster) that the drummers need not move their elbow to raise the sticks higher

8

iDAF-drum: Supporting Everyday Practice of Drum

Fig. 5. Test pieces

for adjusting the impact-impact interval. As a result, we can expect iDAF toeﬀectively make them use the extensor muscle. Conversely, it becomes diﬃcult
for them to greatly exercise the extensor muscle. However, people usually cannot
immediately master such ways of using the extensor muscle: Long-term training
is required. Therefore, it is preferable, from a safety viewpoint, to make them
use this muscle little by little.

5

Estimating Eﬃciency of iDAF-Drum

In the previous section, we showed the possibility that iDAF-drum leads the
drummer to suﬃciently use the extensor muscle. This section investigates whether
the drummer can eventually master the correct drumming way of suﬃciently using the extensor muscle by continually using iDAF-drum. If this can be achieved,
the myoelectric potential of the extensor muscle without delay will increase alongwith the progress of training and ﬁnally become as strong as that with delay.
5.1

Experimental Procedure

In this experiment, we employed ﬁve subjects who are members of a brass bandof a high school and are included in the 12 subjects of the experiment shownin the previous section. We asked them to perform a 10-minute practice session
every day, which includes 2-minute single-stroke practices for the left and righthands, a 3-minute change-up practice, and a 3-minute drumroll of 16th notes(Figure 5). Before starting this session, each subject was allowed a warm-up
performance.
We set the metronome to a 500 msec interval. In the previous section, we
pointed out that it is preferable to set the performance speed relatively fast.

iDAF-drum: Supporting Everyday Practice of Drum

9

However, some subjects did not have so much experience. If we set the performance speed too fast, they might not have been able to perform the test pieces.
Therefore, we examined maximum speed for each subject before the experimentand set the speed as fast as all of the subjects could perform the test pieces.
Under this metronome interval, the speed when 8th notes were performed was
the same as in the experiment conducted in the previous section, and it became
faster when shorter notes like 16th notes were performed. Therefore, the overall
performance speeds of this experiment are faster than those in the experimentof the previous section.
The system setup of iDAF-drum is the same as that used in the previous
section. However, in this experiment, we used two sets of iDAF-drum.
Each subject practiced 10 minutes every day using the iDAF-drum with a 20
msec delay for twelve days. On the ﬁrst day, the sixth day, and the last day, wemeasured the MVC of the extensor muscleof each subject three times, and thenwe asked each subject to continue drumming along with the metronome at 250
msec intervals for 1.5 minutes using iDAF-drum with no delay and with 20 msec
delay. During these performances, we measured electromyogram of the extensor
muscle of both arms together with synchronization signals.
We applied the signal-averaging method to the obtained data to reduce noiseand calculated the root mean square (RMS) of the cleaned myoelectric potential
data between the synchronization signal and 250 msec before that. Then thedata were normalized using the MVC of each muscle so that the MVC value
was set to 100 percent. In addition, for each muscle and for each delay time,
we calculated the accumulated electromyogram data between 30 and 90 seconds
from the beginning and the average of the gross amount of muscle activities ofall subjects.
5.2

Results

Figures 6 and 7 show the averaged electromyograms of the extensor muscles ofboth hands of all subjects with no delay on the three measuring days. In theﬁgures, vertical black lines drawn at 250 msec show the impact timing.
From these ﬁgures, we can see that the peak values became higher day byday. We calculated the averages of the myoelectric potential data between thesynchronization signal and 250 msec before that. The ANOVA for the averaged
myoelectric potential data showed a signiﬁcant main eﬀect of the measuring day
for the left hand (F (2, 12) = 4.815, p < 0.029). However, no such signiﬁcancewas shown for the right hand (F (2, 12) = 2.062, p < 0.170).
A supervisor of the brass band of the high school pointed out that one of thesubject’s drumming sound changed during the experiment: The sound became
sharp and clear.
5.3

Discussions

If the drummer learns how to use the extensor muscle while being forced touse it by iDAF-drum, we can expect that the extensor muscle will come to be

10iDAF-drum: Supporting Everyday Practice of Drum

Fig. 6. Electromyogram of the extensor muscle of the left arm without delay

Fig. 7. Electromyogram of the extensor muscle of the right arm without delay

used even without delay day by day. From the results shown in Figures 6 and
7, although no signiﬁcance could be obtained for the right hand, a day-by-day
tendency for the extensor muscle to be used more without delay was observed.
We should conduct a control experiment by preparing a control group whose
subjects practice using only a normal drum without delay. This time, unfortunately, we could not do so due to the lack of experimental equipment. However,most of the subjects we employed have practiced the drum for a long time (Average: 4.71 years, STDV: 3.29). If such experienced drummers can immediately
master techniques for using the extensor muscle in only 12 days’ practice, we canassume that they have already mastered the techniques. Therefore, it is unlikelythat a control group would show changes within these 12 days. In contrast, we
obtained some evident changes in this experiment. This fact supports the ideathat iDAF-drum is eﬀective for improving the use of the extensor muscle.
All of the subjects were right-handed, and they could use the right handat will. From this, we can infer that they already had some skill in using theextensor muscle of the right hand. This is likely a reason why no signiﬁcancewas obtained for the right hand’s myoelectric potential data (Figure 7). On thecontrary, they could not use the left hand at will in the same manner as the righthand, and they did not have enough skill to use the extensor muscle of the left
hand. As a result, the eﬀect of training by using iDAF-drum clearly appeared.

iDAF-drum: Supporting Everyday Practice of Drum

11

This implication was supported by the result that signiﬁcance was obtained forthe left hand’s myoelectric potential data (Figure 6).

6

Conclusions

In this paper, we proposed iDAF-drum to exploit the eﬀects of insigniﬁcantly delayed auditory feedback in human behavior. Our purpose was to support drummers in mastering the suﬃcient use of the extensor muscle in controlling thedrumsticks. Using iDAF-drum, we conducted user studies and investigated its
eﬃciency. As a result, we found that the subjects came to raise the sticks higher
than usual and that iDAF did not confuse the drummers in their performance.
Furthermore, by continually using iDAF-drum, the myoelectric potential of theextensor muscle became stronger day by day. Consequently, we could conﬁrm
the usefulness of iDAF-drum.
In the case of iDAF-drum, the drummers’ actions changed although they
could not perceive the existence of the delay. We have applied iDAF to a keyboard such as a piano. Similar to the drum cases, performers could not perceive
the delay. However, they reported that its keys were heavier when iDAF is inserted between key-touch and sound emission than those without delay. Thus,
people involuntarily react to the unperceivable factors and they perceived themas a diﬀerent feeling. These phenomena are very interesting. It suggest possibilities of the unperceivable factors that people’s behaviors can be changed without
being realized the existence of the factors by them and we can provide some
diﬀerent feelings without actually changing structure of an object (such as the
keyboard) to provide the feelings. In future, we will further explore other casesthat provide such illusory feelings and apply them for eﬀectively bringing out
and fostering buried creative abilities.

Acknowledgments
We thank the members of the light-music circle of Miyazaki University and thebrass band of the high school associated with Kumamoto Gakuen University for
their kind cooperation to our experiments. We also thank Dr. Kohei Matsumura
of Ristumeikan University for his valuable advices on measuring electromyogram.

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