The problem
Cello is a bow string music instrument of the violins’ family. As all strings, it requires a high level of
accuracy to be played and many years of studying. One of the major requisites for correctly playing it is
keeping the bow perpendicular to the strings.
Especially for beginners, accomplishing this task is extremely difficult because, from the cello player
perspective (while playing), it is hard to understand if it is being done correctly. This skill which requires a
lot of time
and practice to be acquired, up to the point in which the player gets used to it.
Traditionally, this skill is taught by the teachers which warn the students when they are playing the cello with
the bow in a crooked position, and correct their posture while playing, moving their arm accordingly.
Consequently, students practicing Cello on their own, at the beginning, are constrained to play the instrument
in
front of a mirror to see if their movements are right. Thus, to train with the Cello, students would also need a
proper place with enough space in front of the mirror at home, which is not always possible.
In
addition,
properly
learning the correct movement in front of the mirror is not that obvious because of specularity.
Therefore, the use of the bow is the first and biggest obstacle that beginners bump into when
approaching
the cello, which, of course, is also the prerequisite to start playing the cello correctly.
Addressing the problem
Thus, keeping the bow perpendicular to the strings is not an easy task for students. In order to address this
problem, a multisensory interactive system might be the proper solution.
Smart bow provides stimulation through 2 main sensory modalities:
1) A visual interface shows the
inclination of the bow;
2) Two vibration motors placed in the forearm interact with
the user.
In this way, SmartBow gives students feedback on how they are handling the bow with respect to the
strings, helping them correct their movements. In fact, SmartBow leverages visual and haptic perception to allow
cello students to practice on their own in an effective and intuitive way.
Developing such a system is a delicate task, since SmartBow operates in a context of sensorial
saturation:
playing
a musical instrument is a complex task, which already involves many senses at the same time. Thus, after an
initial analysis of the problem, the implementation of an auditory feedback has been excluded, to avoid a
situation of conflict between the feedback itself and the sound emitted by the cello.
SmartBow takes as main input the body movements with respect to the cello, exploiting IMU’s gyroscope
ability to
detect absolute orientation in space. A microphone on the cello also provides auditory input, in order to
correctly detect the string which is being played. As previously mentioned, the outputs are a visual animation
of
the position of the bow with respect to the strings, and a vibrotactile stimulation given by the vibration
motors.
Components’ Communication
Evaluation and test
Once the SmartBow prototype was assembled and after a pilot study was conducted, an experimental step was
organized to test the system.
Our research question was to understand if participants’ interaction with the SmartBow system actually
influences body motion-response and body-perception, improving the user's ability to keep the bow perpendicular
to the strings.
In order to assess the hypothesis, we performed an experiment with the intended users. Unfortunately, due to the
COVID pandemic and its consequences, it has not been possible to engage actual cello students in the
experimentation. However, the testing has been conducted anyway, inviting a sample of 10 young people (100%
under
27 years old).
We structured a within-subjects study design divided in 4 main steps. At the start of the experiment,
participants
had to fill a survey asking them general questions to assess the participants’ impression and familiarity with
the
cello.
Second, participants were asked to try the cello to get familiarity with the instrument and fill the second part
of the survey. Third, they had again to play the cello but with the visual interface of SmartBow activated and,
after that, fill the corresponding part of the survey. Last, participants had to play the cello with both the
visual and the haptic feedback implemented, and, again, fill the survey.
The survey was divided into 5 sections. The purpose was to evaluate if participants felt more comfortable with
SmartBow’s functionalities being activated or not, asking them the same implicit questions after each step of
the
experiment. In addition, each section of the survey had a couple of explicit questions about SmartBow’s
functionalities.
This structure would allow us to both get insights about the explicit perception of participants towards
SmartBow,
and also to compare how they felt during each stage of the experiment.
Furthermore, during each performed task, the number of errors made by the user was counted by the system,
providing us with some quantitative data.
We had the chance to perform the experiment with 10 volunteers. Within our sample, 44% of the respondents had
never played any string instrument, the remaining had tried or played one, e.g. one participant has been playing
violin for 12 years, others play the guitar. Anyways, almost all of the participants stated their low
familiarity
with the cello and consider it as a difficult instrument to play.
