Songs are often built around a basic family of three chords. Different keys rely on different families. The videos below will introduce you to four keys that we often play in on the uke. I think it's really helpful to commit these basic families to memory - not only does it move your musical knowledge forward, but they will help you expand your playing skills, as well. See the bottom of the page for a little challenge related to that.
Key of C - Teach Your Children, by Graham Nash
Family: C, F, G7 (plus Am)
Please note: I flubbed a line on the first chorus! It should be: "Teach your *children*..." I confused it with the second chorus, which begins: "Teach your *parents*..." Apologies!
Key of D - Angel from Montgomery, by John Prine
Family: D, G, A7 (plus C)
Key of G - The Last Thing On My Mind, by Tom Paxton
Family: G, C, D7
Key of A - Blowin' in the Wind, by Bob Dylan
Family: A, D, E7
Now that you've gone on this little "Tour of Keys", let me blow your mind a little. Music is made with individual notes played in a series (aka "melody") and with chords (group of notes played together) that are also played in a series (often called "harmony" or "harmonics") ... but the pattern of a song is really built on the relationship between these notes and chords. If the key of the song simply gives us our starting point, then we can play any song in any key we like, as long as we maintain the relationships between the notes and the chords.
For example, take the last song on this tutorial, Blowin' in the Wind - we played it originally in the key of A with the chords A, D, and E. I could also play it in the key of G, but my chords would have to shift. Here's how:
We're moving from A as our starting point to G as our starting point, so we're shifting "down" one key, because we're moving our starting point to a note that is lower in tone than the original starting point.
Because we've shifted our starting point down one step, we have to do the same with the other chords, in order to keep the relationships intact. So, we shift D back one step to C ...
... and we shift E back one step to D ...
In the key of A, we played the E chord as E7. It's very similar to the plain E chord, it's just made of up of a slightly different set of notes (not important to know right now), and I think it works well to play that third chord of the family as a 7 chord. So, we'll let that "7" travel with the chord and now we've got a new family to play Blowin' in the Wind: G, C, and D7. Sound familiar? Yes, those are the chords we used to play The Last Thing on my Mind.
As I wrote at the top of the page, I think it's worth your while to commit these 3-chord families to memory - not only does it expand your chord repertoire, but, as you can see, it allows you to expand your application of that chord knowledge by giving you the option of shifting the key of any song you play.
Still with me? One last challenge to leave you with: Try playing Blowin' in the Wind in the keys of C and D as well!