The 8038 sine wave VCO has been around for a good chunk of a century. Probably about the same for the XR-2206. But their distortion is in the half-percent range, and I'm desiring a low distortion sine wave VCO with distortion in the 0.01% range (and will not complain if it's better).
For my particular project, I need the center frequency to be somewhere in the low audio range (20 Hz to 1kHz would be great.). I'm not picky about the exact center frequency. I also have very undemanding needs for the tuning range: +/- 10% would be enough, and maybe just a few percent would be better.
DDS isn't particularly desirable because the control voltage is a voltage, not a number. I know I could add an A/D to make it a number, but my feeling is that this is going down the wrong road.
Wien bridge oscillators can certainly meet the distortion needs, but is there a "good" way to control the frequency (even over a limited range) with an external voltage? Again, don't get into digitally-controlled pots. I'm thinking something more like photocells here. But wouldn't I need a matched pair of photocells? If the variable R were only a small part of the total R, matching wouldn't be all that important, right?
Since my frequency range is so narrow, is a 8038 or XR-2206 followed by many poles of low-pass filtering out of the question?