# Creating a Remote Choir Performance Recording Based on an Ambisonic Approach
## 5 Eye-Tracker-Based Examination  
The aim of the designed examination was to check whether eye-tracker technology may be employed in observing performers' divided behavioral attention in the context of looking at the conductor and music notation, both visible on the screen in the network-based environment. This is related directly to the guidance role of a conductor. Secondly, it was to evaluate the aspect of quality of experience (QoE).  
The examination setup was designed to replicate the at-home recording situation. As shown in Figure 3, a typical home-recording setup consists of a screen displaying the conductor's model recording and, at the same time, showing a sheet of music notes. Moreover, participants used headphones to provide auditory input from the model recording. Therefore, the eye-tracked environment attempted to replicate these conditions as accurately as possible.  
Figure 6: Arrangement of the choir on the background of the rendered view of the cathedral interior model [60].  
The testing environment comprised a Tobii EyeX eye-tracker, a PC running Windows 10 along with the eye-tracking software, and a pair of consumer-grade closed-back headphones (namely, Sennheiser HD380 Pro). Moreover, an Apogee ONE USB audio interface was mounted on a tripod, used for convenience, as it has an easily accessible volume knob, so the participants could comfortably adjust the loudness of the audio played back. The environment is presented in Figure 7. In Figure 8, the visual input is shown.  
The examination started with a calibration of the eye-tracker. Then, the audio-visual recording was displayed on the screen, and the participant was performing their vocal part. The recording for the examination consisted of the first page of [PERSON]'s Sicut Cervus and took 57 s in total. The calibration, the video playback, and collecting the eye-tracker data were automated via scripts written in Python 3.  
Figure 9 shows the heat map obtained based on averaging all individual performers' heat maps. The bar on the right indicated the intensity of fixation. It is evident that in the case of the averaged results, the primary focus was on the conductor. The ROI (Region of Interest) is on the conductor's face but less on his hands, which are used to convey expressiveness inscribed within the music notation. This may be related to the properties  
Figure 8: Visual input.  
Figure 7: The setup of the eye-tracking environment.  
of human vision. By analyzing the placement of the test stand in terms of the chorister's field of view (Figure 10), it can be estimated that with a typical distance of the chorister from the screen (\(d\)) of about 60-70 cm and a space between the conductor's hands (\(2w\)) of 20 cm, the chorister's vision focus lies within +/ \(-\) 8-10 degrees. For the calculation of the viewing angle (\(\alpha\)), we used the following Equation (1):  
\[\propto=arc\tan\frac{w}{d}, \tag{1}\]  
Moreover, these angles are similar to the real situation, where the conductor is about 5 m away from the chorister and the distance between the conductor's hands is about 1.5 m.  
Such values of visual field angles suggest that the conductor's hands are on the edge between central and peripheral vision [84; 85]. Thus, by focusing their gaze on the conductor's face, choristers can easily see the conductor's hand movements clearly. Focusing the gaze on one of the hands would definitely make it challenging to observe the other hand (especially while both hands are in motion). Furthermore, following the conductor's facial expressions makes singing easier for choristers [86].  
Figure 10: Spatial relationships between the chorister and the conductor.  
Figure 9: Average ROI for 20 choristers.  
In contrast, Figure 11 shows the individual results of a chorister unfamiliar with the sung piece; hence, this person focuses much more on the right side, where the sheet of music notes was presented. It should be, however, noted that this person has a relatively fluent ability to read music notes _a vista_.