Here are some resources for music and for other sounds:
http://www.openmusicarchive.org
https://www.freemusicarchive.org
Free Sound (for sound buffs, lots of natural and human ambiences, etc.)
Archive.org has a sound archive, and their film archive can be mined for tracks as well…
Sounddogs is a commercial aggregator of SFX. You can download, typically, for free, and then license later if your project requires it.
AUDIO APPS
I found a few audio apps for iPhone that are free.
One is called Voice Record Pro:
https://apps.apple.com/us/app/voice-record-pro/id546983235
A useful app for Mac computers is Audio Hijack. It allows you to record anything going through your computer. I use it in combination with Skype, for example, to record conversations. It is not free. https://www.rogueamoeba.com/audiohijack/
And you can record audio via Zoom. However, the quality may not be ideal.
PDF OF AUDIO RESOURCES:
ARCHIVE RESOURCES
This is a list put together by students and faculty at UC Santa Cruz last year:
Collective Production 