The short answer
Open the Clock app, tap Alarm, tap Edit, choose your alarm, then tap Sound. Pick any built-in tone, or scroll to Pick a Song to use music from your library. Tap Save. The change applies to that alarm only, not all of them.
Change the tone on an existing alarm
- 1Open the Clock app and tap the Alarm tab.
- 2Tap Edit in the top-left, then tap the alarm you want to change.
- 3Tap Sound.
- 4Choose a tone. The list is split into Ringtones at the top and Songs beneath. Tap one to preview it.
- 5Tap Back, then Save.
Use a song as your alarm
- 1Follow the steps above as far as the Sound screen.
- 2Tap Pick a Song at the top of the Songs section.
- 3Browse or search your library and tap the track you want.
- 4Tap Back, then Save.
Choosing a sound that keeps working
Most people change their alarm sound because the old one stopped working. It usually has not: you have habituated to it. Your brain learns to categorise a familiar sound as unimportant, and filters it out during light sleep.
- Rotate sounds every few weeks rather than searching for one perfect tone.
- Prefer sounds that build gradually. A sound that starts quiet and rises wakes you with less of a jolt and is harder to sleep through than a constant tone.
- Avoid music you love. You will start to resent it, and familiar music is the easiest thing of all to sleep through.
- Avoid sounds resembling something normal in your environment — birdsong is a poor choice if you have birds outside.
If you have already rotated sounds and still sleep through them, sound is not your problem. Habituation applies to volume as well as tone, which is why "just make it louder" stops working too. At that point the thing that changes outcomes is requiring an action rather than a tap — see our guide on alarms for heavy sleepers.