Wavelength of 2600Hz at 44100Hz sampling rate would be slightly under 17 samples, so any repeating string of 17 single-byte characters would do (44100/17 = 2594Hz, dunno if that's close enough). Or 34 or 68, depending on whatever is playing it expects stereo and/or 16-bit data.
Unless the higher harmonics (5200Hz, 7800Hz, etc) mess up the tone (no idea how strict the old 2600Hz hack used to be). In which case you need some characters that approximate a sine wave. Which isn't too hard, given that you don't care about DC bias and max amplitude.
Unless the higher harmonics (5200Hz, 7800Hz, etc) mess up the tone (no idea how strict the old 2600Hz hack used to be). In which case you need some characters that approximate a sine wave. Which isn't too hard, given that you don't care about DC bias and max amplitude.