OFICINA DE SUPERVISIÓN Y LIQUIDACION DE OBRAS

Movement imitation has been crucial in the performances registered for the harmonization task in the second session test. The mere observation of the movements of the test conductor while performing the harmonization task has been able to transmit only by imitation and in a very short time a lot of information to the test subjects. As a matter of facts, the only clear effect of the treatment is the improvement of the instructed group in the harmonization task, as shown in Table 7.12, where it is clear that the lack of a practical example of melody harmonization makes the difference. Many other information has been delivered during the one hour lesson administered to the instructed Musicians and Not Musicians group. However, explicit information has proved not as effective as movement observation and enactive learning.

Chapter 8

Harmonic Walk Interface Test

Two different tests are presented in this Chapter under the common label of Harmonic Walk interface test. The first test concerns the effects on user’s performance of the chord spatial ar- rangement on the Harmonic Walk active floor surface. Two arrangements are proposed and the user’s performance is measured under the two different conditions. The second test compares user’s performance and preferences with respect to the song harmonization task on the active floor surface and on a touch screen. The results show that the physical effort implied in full-body interaction plays an important role in movement pattern memorization and that, in spite of the playful approach proposed by the active floor interaction modality, users perform better on the touch screen and prefer this latter to full-body interaction. These results are very important for the design of interactive spaces applications, as they offer meaningful perspectives regarding the role of full-body interaction in these environments.

8.1

Harmonic Walk Chord Arrangement Test

The Harmonic Walk chord arrangement test aims at verifying the effects of chord spatial ar- rangement on user’s performance. Two arrangements are tested. Arrangement 1 derives from the tonnetz’s tonal harmony spatial representation discussed in Section 5.1.5, which is an abstract spatial rendering of the chord relationships grounded on renowned theoretical and perceptual basis. Arrangement 2 is built following opposite criteria than those arising from the tonnetz. In arrangement 1 the three main roots (in red in Figure 8.1) are grouped in a half of the circular ring, and the parallel roots (in blue in Figure 8.1) in the other half. The main and parallel harmonies are well separated and each parallel root is put in front of its main as shown by the white lines. Arrangement 2 on the contrary disrupts completely the circular ring division between main and parallel roots and the position’s reciprocity of a main root with its parallel. Moreover the most used chord progression (I-V degree) has the shortest step length in arrangement 1 and a medium step length in arrangement 2. The experimental hypothesis is that the group of subjects trained with arrangement 1 should benefit of its spatial and perceptual qualities and thus perform better that the group trained with arrangement 2.

118 Interactive Spaces: Models for Motion-based Music Applications

Figure 8.1: The two chord arrangements employed for the Harmonic Walk interface test. The red circles are the main roots and the blue are the parallel. The straight, dashed and spotted arrows indicate respectively the shortest step lenght (1), the medium (2) and the longest (3).

8.1.1

Subjects

A total number of thirty-two elementary school girls and boys between ten and eleven years old took part in the test. The students are equally subdivided into two different groups of sixteen subjects each: one group is trained with arrangement 1 and the other with arrangement 2. All subjects have no musical instrument training in their school curriculum.

8.1.2

Materials

The test is based on a simple children song. To guarantee a uniform level of song knowledge from the subjects, the song has been expressly composed for the test. The required musical characteristics of the song are the following:

a) the melodic movements must be reduced to the minimum;

b) the harmonic rhythm must be regular, without harmonic syncopations;

c) the harmonic progression must include at least one main chord (beyond the first degree) and one parallel chord;

d) the melody should employ preferably repeated patterns;

Chapter 8. Harmonic Walk Interface Test 119

Figure 8.2: The melody employed for the Harmonic Walk chord arrangement test. The song text is reported together with the harmonic changes.

Song semi-phrases SP 1 SP 2 SP 3 SP 4

TOTAL EFFORT Harmonic Changes I V I V ii vi ii vi I V I V IV I V I

Step length arr. 1 - 1 1 1 3 1 1 1 3 1 1 1 2 1 1 1 20 Step length arr. 2 - 2 2 2 1 3 3 3 2 2 2 2 1 3 2 2 32

Table 8.1: Table of user’s efforts in harmonizing the melody for the Harmonic Walk chord ar- rangement test.

Three proposed melodies have been analyzed by four musicians experienced in test management. The melody chosen for the test is depicted at Figure 8.2 where the song’s text and harmonic changes are shown. The song’s harmonic rhythm requires one harmonic change for each of the sixteen song bars. The changes are regular and are organized in group of four bars (musical semi-phrases, SP from now on). SP 1 is I-V-I-V with all the harmonies in the main root area. SP 2 is ii-vi-ii-vi with harmonies in the parallel root area, SP 3 is again like SP 1 and SP 4 is IV-I-V-I with harmonies in the main root area. To obtain a measure of the overall user’s physical effort spent in arrangement 1 and 2, a number related to the step lengths involved in the two arrangements is provided at Table 8.1. With reference to Figure 8.1, step lengths are calculated as 1 (straight arrow, shortest length), 2 (dashed arrow, medium length) and 3 (spotted arrow, longest length). The step length calculation results report an overall effort of 20 for arrangement 1 and of 32 for arrangement 2, with a difference of about the 30% for the benefit of arrangement 1. Moreover, the step lengths occurrences shown in arrangement 1 are disrupted in arrangement 2. Particularly, the change of harmonic zone is marked by a 3 or 2 in arrangement 1. The zone change is followed by a series of 1, which points out that when a zone is reached the movements inside it are as short as possible.

8.1.3

Method

The control group is assigned arrangement 1 and the treatment group is assigned arrangement 2. Preliminary tests have been organized to verify if the chosen melody fits the tests requirements, and if the test procedure has the right event sequence and timing. Moreover, two experts perfor- mances have been recorded to be employed as mean reference times for subjects’ performances

120 Interactive Spaces: Models for Motion-based Music Applications

evaluation. The test is subdivided in three sessions:

1. First session: one hour class lesson about harmony and melody accompaniment. The aim of the lesson is to teach the movement pattern related to the song harmonization to the children. During the lesson the song chosen for the test is used and repeatedly sung by the teacher and pupils. Games on the song’s harmonization, chord progressions and harmonic rhythm are proposed. Movement games where students move in time with the harmonic changes are performed following the chord arrangement assigned to each group. The lessons are carried out in separate sessions for group 1 and group 2, because the chord arrangement is different for the two groups.

2. Second session: one hour training in the test laboratory where children learn how to in- teract with the Harmonic Walk active surface and what is the sound produced by their movements. A touch screen version of the active floor is also presented and tested by the children. The second session is carried out in separate sessions for group 1 and group 2, as for the first session.

3. Final session: individual ten minutes test. The final session of the test is carried out in a laboratory, one subject at a time through a semi-automatized procedure. Only the test conductors are present in the laboratory. The subject is introduced in the test laboratory and is asked to answer a pre-test question about application’s pleasantness. A pre-recorded virtual voice drives the subject through the various phases of the test, whose progress is determined by the test conductor. First the subject is invited to explore the environment and listen to the sounds of the various chords. Then the system performs a piano-only version of the song and invites the subject to sing it. At last, when the song has been recalled to the subject’s memory, a recorded audio file with only the melody is played while the subject has to harmonize it by moving on the active surface. Three trials are allowed to the subject, which continue until the end independently from the quality of the subject’s performance or mistakes. At the end the subject is asked to answer a post-test question about application’s pleasantness and to complete a questionnaire (see Section 8.3).

All the sessions of the test have been organized at a time interval of at least fifteen days.