I think a few people will like this, a really great sounding tremolo. The 2N2646's are obsolete but still available from a number of places, RS, Farnell, Mouser and a few sellers on eBay. They're not as cheap as the more common silicon transistors but definitely worth getting in for this.
Modified to include a depth pot and altered values for more output.
Version with all of the above and a couple of extras including a Tone switch which switches the input cap to give you an option to prevent any low end loss, and a Fast/Slow rate switch.