Both definitions, one and two below, would seem to make the disputed application of "musical" acceptable.
#1 suggests it need not produce music. Being of or pertaining to is sufficient.
#2 However successfully it accomplishes the task, what comes out of my speakers resembles music to me.
Is anyone still confused?
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mu·si·cal /ˈmyuzɪkəl/ Pronunciation Key - Show Spelled Pronunciation[myoo-zi-kuhl] Pronunciation Key - Show IPA Pronunciation
adjective 1. of, pertaining to, or producing music: a musical instrument.
2. of the nature of or resembling music; melodious; harmonious.
3. fond of or skilled in music.