In lesson 2 we learned how to play the C major scale in "open position". That means that instead of playing the whole scale up to C string we use the open E and A strings where we can. It goes like this.
C string: C, D
jump to E string: E, F, G
jump to A string: A, B, C.
And you're done!
Students were asked to take the kids songs that they had learnt by ear on the C string and play them now in "open position." This can be a convenient way to play a song because you don't have to jump around the neck of the ukulele as much.
However, most people find it easier to figure out things by ear going up and down one string because they don't have to deal with the leaps between strings.
In the second half of the second class we talked a little about these weird numbers I, IV and V. We played Louie Louise using the notes C, F and G from the C major scale. C is the first note in the scale, F the fourth, and G the fifth. These are the root notes of the chords in the song.
If we create chords on these root notes we get: a C chord, F chord, and G chord (G7 works too). We call the C chord the I (roman numeral "one") chord because it's root is the first note in the scale. F chord is IV and the G chord is V because the roots of those chords are the 4th and 5th notes in the scale. So, the C chord, F chord, and G chord are the I, IV and V chords from the scale of C. (You could also say "in the key of C"). Also note that the V chord is very often a V7. So that makes I, IV, V7 in the key of C these chords: C, F, G7.
The song Jambalaya uses the I chord and the V7 chord from the key (scale) of C. These chords are C and G7
Now some people found Jambalaya difficult to sing in the key of C so we moved the song to the key of F. In the key of F, the I (one) chord is an F chord and the V7 chord is a C7.
Hope that helps!
A quick note. If you are interested in pursuing music theory there are some quite good books out there.
Jim D'Ville The Natural Way to Music
Idiot's Guide to Music Theory (I always get a chuckle recommending this book. A surprisingly good book)
Also these links are worth exploring.
http://en.wikipedia.org/wiki/Chord_progression#Simple_progressions
http://www.balladtree.com/folk101/g_001a_chords.htm
