The answer is simple in that there is very little you can do apart from set the recording levels carefully. If the record level is too high, then the peaks of your recording will be clipped and the signal will sound harsh.
Most recorders have a record level meter that is often labelled in 'VU' or volume units.
On this scale, a value of 0dB represents a safe recording level. However clipping does not normally occur until about 3-6dB above this level. Thus you should aim to make your recording peak close to but below 0dB VU, and use the extra headroom for the occasional loud noise that might occur. Normally, by distortion, we mean the introduction into our signal of frequency components not present in the original. Timbre is the third dimension of our perceptual sensations of sound.