I don't know that much about Chinese music, but a couple of things I do know:—

You shouldn't have to retune your guitar at all. The Chinese use the same notes we do, not counting transitory slides from one note to another. Western European music uses these slides too, but not quite as much as Chinese music. It's just that in five-tone (pentatonic) scales, you obviously don't use all the notes to be found in the standard Western major or minor scale. There are several possible pentatonic scales and it would be necessary to know which one or ones the tunes are in. The best I can suggest is, if you have the tunes firmly in your ear, just fish around on the guitar—trial and error—until you find which strings and frets the notes you want are on, then it should be duck-soup.

One thing that characterizes pentatonic scales is that there are no half-steps. They are composed of whole steps, or intervals of a step and a half. A typical pentatonic scale would be A C D E G then a repeat of the A an octave above the first A. Another is C D E G A and a repeat of the C, which is exactly the same, but starting and ending on a different note. The black keys on the piano form a pentatonic scale, and you can probably play a lot of Asian music on them. A lot of Scottish music, much of which is pentatonic, as well.

As to chords, that gets a bit tricky. Ideally, you wouldn't want to use any notes in the chords that you aren't using in the scale, but with the standard chord families, that's next to impossible. In the two examples I gave above, try to stick pretty close to the C and Am chords in both. You can try playing parts of other chords, like a G, for example, playing only the G and D notes and avoiding the B. You'd have to pick individual strings or pairs of strings rather than strumming. The two notes you want to avoid in this case are B and F. As I say, a bit tricky. It's a matter of experimentation. Try other closely related chords and see if they sound right. That's about the best test.

That's not much to go on, but I hope it helps.

Don Firth