654 Category: Human Aspects of Technology Computer Music Interface Evaluation Dionysios Politis Aristotle University of Thessaloniki, Greece Ioannis Stamelos Aristotle University of Thessaloniki, Greece Dimitrios Margounakis Aristotle University of Thessaloniki, Greece Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited. IntroductIon The old computing is about what computers can do, the new computing is about what people can do. Ben Schneiderman, HCI Researcher (1997) One of the most intriguing ields of human-computer interaction (HCI) involves the communication aspects of computer music interfaces. Music is a rich communication medium, and computer music is the amalgam of interface science and musical praxis forming a dynamic subset of HCI. There are structural similarities between the job of a music composer and that of a user interface designer (although their objectives may be different). While sound has been used in general purpose interfaces as an object, its use has been deteriorated at a primary level, that of a signal-processing approach. However, music composition and performance are highly abstract human activities involving a semantic and a symbolic mechanism of human intellectual activity. This article analyzes the unique problems posed by the use of computers by composers and performers of music. It presents the HCI predicates involved in the chain of musical interaction with computer devices, commencing from the ab- stract part of symbolic composition, then coping with usability issues of the graphical user interfaces (GUIs) implemented for musical scripting, and concluding to a synthesis stage which produces digitized sounds that enhance or replace original analog audio signals. The evaluation of HCI ele- ments for computer music under the prism of usability aims at the development of new graphical tools, new symbolic languages, and inally better user interfaces. The advance in technology on this area creates the demand for more qualitative user interfaces and more functional and lexible computer music devices. The peculiarities of computer music create new ields in HCI research concerning the design and the functionality of computer music systems. Background computer music Interfaces In the early stages of the microcomputer evolution, various protocols had been developed in order to achieve intercon- nection between computers and instruments. The milestone of computer music proved however to be the musical instrument digital interface (MIDI), which is a communications stan- dard used for transmitting musical performance information (Aikin, 2003). It was developed in 1983 in response to the increasing sophistication, and corresponding complexity, of commercial electronic instruments, especially synthesizers. Therefore, MIDI is a protocol specifying how electronic musical instruments may be controlled remotely. In brief, MIDI is a very successful and inexpensive protocol that has reshaped the computer music landscape. However, it cannot overcome easily its representation limitations, especially on alternative music notations. The common music notation (CMN) scheme along with the MIDI speciication is Western music oriented. The problem with CMN has been taken into account in several works: Although CMN is supposed to furnish a model for traditional music in a European style, it is not absolutely supposed that this model is also convenient or suitable for music coming from outside ofWestern traditions (East Asia, Middle East countries, etc.) (Bellini, Barthelemy, Nesi, & Zoia, 2004). As a result, they are not able to clearly depict alternate musical forms and traditions. Almost all music recordings today utilize MIDI as a key enabling technology for recording music. In addition, MIDI is also used to control hardware including recording devices as well as live performance equipment such as stage lights and effects pedals. Lately, MIDI has exploded onto the scene with its adoption into mobile phones. MIDI is used to play back the ring tones of MIDI capable phones. MIDI is also used to provide game music in some video games. MIDI is almost directly responsible for bringing an end to the “wall of synthesizers” phenomenon in 1970-1980s rock music concerts, when musical keyboard performers