Best timbre for voice training?

So, I've decided to master a few handfuls of tetrachords, at
least to start. Then, like the Turks, I can mix and match upper and
lower tetrachords as I see fit.

Rather than sit at the keyboard all the time I was thinking
I'd burn a CD of the exercises for me to sing along with and repeat.

I believe I should avoid a piano sound for singing with, but
the other end, a sine wave, is very difficult for me to track. Any
suggestions?

--
wm,
breaking out in goosebumps from the high soprano part in Allegri's
Miserere Mass coming forth from my studio monitor speakers as I type...

Hi William,

Sounds like you want a timbre with exact integer harmonics! Not too hard to
find . . .

I rather like the rectified sine wave timbre I used for my listening
examples. The amplitude of the nth partial is less than 1/(n^2) times the
amplitude of the fundamental, yet the tone is "coherent" enough so that
small deviations, either harmonic or melodic, are quite easy to hear.

I found that timbres where the amplitude of the nth partial approached 1/n
for large n sounded too "buzzy" for my taste.

-Paul