a fine line

a wizard is to a witch
a hound is to a bitch
a hobby is to a niche
a nuisance is to enrich 
a silence is to a snitch
a song is to a pitch
a drawing is to a kitsch
an itch is to a twitch
a knot is to a stitch
a ride is to a hitch
a poor is to a rich
a flaw is to a glitch
an absence is to a ditch
a fine line to by which
a routine makes a switch