I'm building a voice ring modulator. Part of it involves a 30Hz carrier sine wave to modulate the voice with. Since I'm trying to build a portable device it will be DC powered, and since a function generator is not really portable or DC powered, I don't thinks that's an option.
Crystal oscillators work at the MHz range so I'm guessing that's not the way to go either. I could play a 30Hz wave on an old mp3 player and use the audio output, but if there's another way involving analog components that'd be much better. There's no need for a lot of accuracy, just any wave from 20-40Hz will probably do, I would say it doesn't even need to be really stable either.
What approach can I take?