DLSTR,

Take the cab downtown ... to the Orpheum. From here you are at the intersection of Beale St and the trolley line.

Maybe hop on the trolley ($1 fare), ride the loop to get a good view of downtown and The River.

Get off the trolley after finishing the circuit and head east up Beale St. From here you can either get some good food at Blues City Cafe, for instance, or go a block South to the Gibson Guitar factory and Rock & Soul Museum ... the museum is actully pretty good and worth the visit. It'll take you at least two hours to do it justice.

Enjoy!