system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is customer service waiting music on the phone so low quality?
gpt
Phones don't send audio at very high quality, just enough to allow you to understand what the other person is saying. In particular, a very common standard for phone call audio is 8 kbps, meaning you only get sound frequencies from 0 to 4000 Hz.

Now, 4000 Hz may seem pretty high (you can look it up), but all kinds of instruments and voices emit "harmonics", which means superposition of different frequencies. So even lower "pitches" can contain frequencies above 4000 Hz. 

When you transmit audio over a phone, frequencies above 4000 Hz are cut, which not only cuts very high frequencies, but also "removes harmonics", making music sound "weird".