In 1981, North Texas State University (NTSU) conducted an experiment in sound sources which was made possible by a grant from the Apple Education Foundation. The culminating research of the grant was the testing of the AFL sound source and Micromusic sound sources, as well as the NTSU sound source, AMUS. Students participated in the experiment to determine relative effectiveness of the sound systems in an ear-training computer assisted instruction (CAI) environment. The experiment was designed over 2 semesters using 36 freshman students to test the three software sound sources in terms of their achievement and preference. It was found that, while students have definite preferences for differing sound sources in music CAI, their preferences correlated most closely with their achievement in a given curriculum area rather than with the sound source itself. The four appendixes contain printouts of lessons used in the experiment; a technical description of the headphones used, written by David Bradfield; a diagram of the Apple Grant Experimental Design; and a copy of the Apple Grant Experiment Participant Sheet. (Contains 9 references.) (ALF)