Hi Kevin and others,
The following applies to a Hohner Piano 36.
I have noticed lately that if I have my mic (a Sure SM 57) on the left side of the keyboard, the amplified sound is brighter and has more harmonics. If I have the mic on the right sight of the keyboard, the sound is louder, fuller, darker, smoother, and has fewer harmonic overtones. I prefer the latter but will use both positions depending upon the sound I want.
The above observation suggests that when recording or amplifying a melodica, one should try different microphone positions. The difference in tonality can be significant.
When the mic is on the right side, it tends to get in the way of playing.