Why do musical instruments have different colour in phone?
Typical telephone codecs use a sampling frequency of 8kHz and a bandwidth of 7kHz.  That means that your signal will get cut off at frequencies higher than 3.5kHz.  That's ok for most speech but not sufficient for reproducing the timbre of most music instruments.

You'll likely fare reasonably well with instruments like recorders (which don't have a lot of overtones).  The worst combination is high-pitched and overtone-rich, like violin, oboe, soprano sax.  Also instruments with a full spectrum will sound different, like high hats, snares, gongs.