: That’s known as the Nashville numbering system, and Phil’s right, mostly, although as I understand it you don’t use Roman Numerals, just regular Arabic #s. The Roman numerals tell you what fret to put a Capo on, which if you’re using the Nashville System, you don’t specifically need to be told that, instead of saying Capo II, play like it’s in G, they’ll just say it’s in the key of A and here’s the progression, 1 / 4 / 1 / 5 / 1 / 2 / 3 / 6m / 2(7) / 1 : In A that’s the following chords : A / D / A / E / A / B / C# / F#m / B7 / A : It’s a pretty cool system if you know how to use it (I’m not fluent or anything). Also to remember, they have special signs for augmented, diminished, suspended and other jazzy chords, or sometimes they’ll just write aug, dim, etc. yep, they call it Nashville, dont know why cause as long as I remember we use it here in Holland. lets play a "one four five" means: lets play a pentatonic blues.. : : What kind of numbers were they? Roman numeral, or digit. My guess is that somewhere at the beginning the key of the song was given and the numbers you see represent the chords in the different degrees of the key scale. Let’s say the song was written in the key of D Major and you see a "1" or a "I" and then you see a "5" or a "V" and then you see a "2" or a "ii". The numbers stand for a D major chord, an A major chord, and an E minor chord, respectively.