Theremin-like device, tone box?

Hi everyone, first post here, complete novice with electronics and instruments. Been trying to find a device vaguely similar to a theremin that plays a steady note, and has knobs to adjust frequency, pitch, and volume.
I dont even know what one would call this but I'm looking for a box like this that I could hook up to speakers, preferably without an amp between them.

heres hoping!

Hi niggles.

http://en.wikipedia.org/wiki/Signal_generator

Music From Outer Space's Weird Sound Generator (http://www.musicfromouterspace.com/analogsynth/YOUR_FIRST_SYNTH/WSG_Reborn/WEIRDSOUNDGENERATORREBORN.php?page=WSG) seems like it could be the ticket. It would be more fun than a signal generator. You can build them yourself or purchase kits or buy a complete one. I don't believe they have a volume knob but that is easily remedied. People have devices similar to this on ebay all the time.

Hi!
Thanks for the help, yes this seems along the lines of what I want, something that can generate sound waves from low to high frequency with output plugs, I was looking at audio signal generators but they seem to be in the hundreds of dollars, and the weird sound generator looks like a lot of fun but a bit excessive for what I want (not to say i wont impulse buy it in the next hour) but if anyone knows of a simple product that meets my needs I would be a very happy person who still only has half an idea what he is talking about. :)
thanks everyone

Something like this might be what you need..

Function Generator $15 simple kit (http://www.electrokits.com/electronics/measurement-test-equipment/61.htm)

better, $21 (http://www.quasarelectronics.com/smart-kit/1008-af-function-generator-20hz-20khz.htm)

Thanks that is almost exactly what i want. (I Think)
Im going to get one and then Ill find out!