12 Bar Blues Backing Track In A Major

Hi there.
This is a guitar backing track, but play your Ukuleles over it, its cool.
The chord progression is a I IV V progression in A major, which using our Handy Dandy Inbuilt Chord Progression Calculator, or as I like to call it our Left Hand, means our Thumb is The Home Chord or I chord of A.
Count fingers up to the 4th finger ie A B C D and ta da our chord calculator gives us the IV chord of D and one more finger along and hey presto there is the V chord or E.  
Make em all 7th chords, or some 7th and some majors, mix it up have fun, experiment.
Listen/feel for the changes and the way the song feels resolved back to the I chord of A.  Keep counting and Jam On Ukers.
Cheers CC