This is the equation of kamma vipaka as I understand it. (Kamma generation of course happen via akusala PS cycle.)
===
A (effect) = { B + C + D + E + F } causes
where,
A = vipaka (effect) = resulting music in radio
B = Physical environment = Body = Radio itself = determines range of available frequencies
Deva/Brahma body wouldn’t be able to manifest kamma bīja suitable only for humans or lower realms.
humans would not manifest vipaka of lower realms.
C = Mental environment = Mindset/Bhava = Tuning of radio = determines which station is tuned
Arhants would not kill anyone, even if they might come across someone who had violently killed them. Because, they have eradicated all the bad bhava.
D = Surrounding environment = Kind of beings around us and their mindset = Location of radio = determines what radio stations are in range and what radio stations are not available
If you are in a monastery full of ariya, you will mostly manifest good kamma/merits.
E = kamma bīja/kamma viññāṇa = Various Radio stations broadcasting signals at different frequencies
F = unknown complex variables discernible only to Buddha
===
Vipaka in a nutshell, can be compared to resonance (Resonance between the overall environment and previous kamma seeds.)