This song was written on a tenor guitar. It ended up being played on a mandola.
It was a period when I almost exclusively played the mandolin and all its siblings in the mandolin family: octave mandolin, mandola, mandocello and Tenor guitar since it is tuned like a mandola (CGDA).
The instrumentation is basically the tenor guitar/Mandola doubling for the riff in the verse and the descending line in the chorus.
The mandolin is featured in the instrumental break of the song.
Check out the MP3 for this on my Open Up Your Heart Music Page