Mono is the simplest approach to both recording and reproduction. A single microphone records the entire sound field, and the recording is reproduced through a single loudspeaker.

This eliminates any means of positioning sound sources, so there is no spatial imaging on playback.

While mono can work fine for speech, solo singers and single small instruments such as the flute or trumpet, it's less well suited for grand pianos and poor for big bands and symphony orchestras. The effect is to squash the whole orchestra into a box the size of the loudspeaker, so important cues can be lost. The classic demonstration of this limitation is a mono recording of an opera scene in which someone walks heavily across the stage. On mono playback this appears as no more than a series of thumps, as of someone stamping on the spot.

However, the famous bird call recordings made by Nicholson and Koch for the BBC in the 1940s and '50s were all in mono, and are superb, as they are mostly near field recordings of single birds. But for wild soundscapes, where the spatial component of the sound field is a major contribution to the ambience, mono is not so satisfactory. Nevertheless, if you're primarily aiming to have your recordings broadcast over radio, you should either record in mono or, ideally, record using a microphone setup such as mid-side that permits reduction to mono.