The great advantage of recorders is that they are fully chromatic, though as usual some keys are easier to play in than others.

For folk music I usually play Mollenhauer dream recorders. They have standard Baroque fingering with the normal two+ octave range but with a wider bore - a bit more like a renaissance recorder - which gives them a little more power than a standard baroque recorder. They also have good tone - which many folk have commented on.

As to harmonicas, I use standard 10 hole diatonic harmonicas with the three blow reed tuned up a tone - this is known as "Paddy Richter" tuning and it gives you the missing 6th degree of the scale below the tonic. It also allows you to play the relative minor chord of the key the harmonica is in.

Paddy Richter tuning for a C diatonic harmonica is

  Hole: 1 2 3 4 5 6 7 8 9 10
  Blow: C E A C E G C E G C
  Draw: D G B D F A B D F A
  

The retuned 3 blow note makes the normal 10 hole diatonic harmonica much more useful for folk music.

Geoff