A predeliction for open and parallel fifths - another Christmas spirit piece: Malpas Wassail by The Watersons

Open-fifths, or bare-fifths are the chord made by an octave with just the fifth note in the middle - for example C-G-C. I developed a great liking for this - mainly because it created what I thought of as a 'medieval' sound - and partly because it is disliked by mainstream classical compositional theory yet seems quite natural to amateur/ folk composers.

I first knowingly came across it in a Steeleye Span song - The King - it was pointed out by my school music teacher:

The drones of a bagpipe or hurdy gurdy are (usually) open fifths. They create a space within which the melody moves. 

This led onto a special liking for the use of parallel open-fifths - when two parts move in-parallel a fifth apart; as used in the early parts of the Tallis Fantasia by Vaughan Williams (parallel fifths are usually regarded as incompetent part writing in classical music - and often they are!):

But my favourite was to use a bare fifth as the cadence - the final chord - of some kind of unaccompanied harmony - as with the middle of the chorus from Malpas Wassail by The Watersons - the bit where the tenor slides up onto the high falsetto top note - which I found, and still find, electrifying.

Indeed the practice of sliding ('portamento') between notes, and chords, with all its dissonances-in-passing, is a marvellous aspect of some vocal folk music: