Minor scales sound different from the major scale that you are used to. There are actually several different types of minor scale but we will look at the most common - the harmonic minor scale. Listen to the difference.
Most of the songs you sing will be in major keys. Probably only about 5% of songs arranged in a barbershop style are written in a minor key (I made up that number but it sounds about right to me!). So most of the time, you are safe in assuming that what you have studied until this point will give you the correct key.
The key signature for a major scale is three semitones above the keynote of the corresponding minor scale.
So if a key signature has no flats or sharps it is probably C major but it could also be A minor.
I remember the word "Canada" to remember minor keys. Canada is a country so is always written with an upper case C (to remind me of the 'Major' scale C major ) and the last letter of the word is a lower case 'a' (to remind me that 'A minor'' is the relative minor) for that key. That is usually enough information for me to remember to go down 3 semitones to get from any major to minor key (although some people remember a word for every one)
If a key signature has one flat it is probably F major but it could be D minor etc
So how would you know whether the song is in a major or minor key?
Songs in minor keys are said to sound sad, sinister or melancholic.
There another rule about harmonic minor scales - the seventh note always has an accidental sharp written next to it (not part of the key signature) so if you suspect that the music may be in a minor key (because it sounds sad, sinister or melancholic), look for any sharp accidentals and see if they would be on the seventh note of the relative minor scale.
And one final clue. Many pieces of music, in both major and minor keys, (but not all - let's say 70%) start and end the tune (so in the case of barbershop, that is usually the lead part) on the pitch of the scale. So, for many songs the lead singers start singing on pitch (making their lives much easier than the other parts because they just sing the note played on the pitch pipe). So in your decision on whether a song is in a major or minor key, look at the lead's first and last notes. If either or both are the note that would be the minor key's first note, that song 'might' be in a minor key.
Have a go at working out minor key signatures
A fun song for remembering intervals by Django Bates
This is the last lesson in your 12-week online course.
If you would like to get some recognition of all your hard work. There is a sample test (pdf) here. If you would like to arrange to take the 'real test' and get a certificate, ask your director to appoint an examiner and ask the examiner to contact me.
I hope you have enjoyed the course.