My idea of pleasing hold music is that it should be soothing, happy background music that is non-distracting, so you can continue working while waiting. But it should be interesting to listen to if you choose to listen, at least for brief snippets. The category “repetitious new age music” fits somewhat.
It should also sound decent on narrowband POTS (plain old telephone service) audio frequencies of 330 Hz to 3400 Hz.
My composition is comprised of 7 instruments playing 7 repeating parts at different cycles in C Major. The repeating parts are unpredictable enough to be interesting, yet predictable enough to be familiar. There is no melody to distract the listener. Just repetitious new age music.
Although the recording uses the full audio spectrum, I listened to it through a 300 to 3400 Hz filter to ensure it would sound adequate on a telephone line.
The track cover art is a self-portrait while listening to hold music too long.