The Pentatonic Scale uses the scale degrees "do, re, mi, sol, la." It can start on any note, but an easy way to work out the pentatonic scale is to play on the five black notes of the piano. If you can play a tune using only the black notes, then the tune you are playing is pentatonic. Tradition says that the slave musicians of the American deep south, used the Pentatonic scale to compose because they wanted to use just the black notes on the piano. That may or may not be true, because the Pentatonic scale was already widely used for centuries before the piano was even invented. Some of the most beautiful folk melodies of that era use the pentatonic scale --- "Swing Low, Sweet Chariot," "Nobody Knows the Trouble I've Seen," "Go Tell It on the Mountain," and "Poor Wayfaring Stranger."
One of the most poignant and beautiful hymns borne out of the of the terrible slavery period is also built on a pentatonic scale -- "Amazing Grace." It comes from the United Kingdom where the pentatonic scale was widely used in folk tunes, hymns tunes and even Nursery Rhymes. The pentatonic scale requires no elegant and sophisticated harmonic accompaniment. In fact, many bagpipe tunes are pentatonic because they work well with the simple drone harmony of a perfect fifth. "Scotland the Brave" and "Loch Lomond" are examples of famous Scottish Pipe songs built on the pentatonic scale. Interestingly enough, some very old English Nursery Rhymes have Pentatonic melodies attached to them -- "Pop Goes the Weasel" and "Deedle, Deedle Dumpling My Son John."
Many beloved American folk tunes and hymns are based on the Pentatonic scale. Here is a short list: "When the Saints Go Marching In," "How Firm a Foundation," "How Can I Keep From Singing," "Come Thou Fount of Every Blessing," "My Shepherd will Supply My Needs," "Zion's Walls," "Take Time to Be Holy," "Camptown Races," "Old Dan Tucker," and "The Arkansas Traveler."
The Pentatonic Scale is fun to improvise around. As I used to tell my school students, "There are no wrong notes." I had my husband make a set of stringed instruments for the classroom. They resembled an Asian zither. They only had five strings tuned to D E G A B which is a Pentatonic scale using the scale degrees (lowest to highest) "sol la do re mi." We also used chimes and Boomwhackers and the Piano to provide drone accompaniments on an open Fifth. Then we wrote on the board little melodies using simple rhythms and turned the class loose to have fun. Even if some wrong pitches or rhythms were played occasionally, it still sounded good. In a Pentatonic scale -- THERE ARE NO WRONG NOTES!