BUILDING THE MBIRA
(3) 10/32 tee-nuts (pronged metal washers with threaded column)
(3) 10/32 x 1 1/4" machine bolts
(1) Piece of cardboard to use as a work space
(1) Small piece of plywood to use to push the metal keys when tuning
Phillips head screwdriver
(2) Mbira Diagrams
Drive the three tee-nuts into the back of the soundboard. Use the cardboard as a cushion. Hammer the tee-nuts until they are flush or just about flush with the surface of the wood.
(SEE PHOTO #1)
Nut & Bridge
Place the wooden nut and the metal bridge in place by centering each between the small HOLES located across the top of the soundboard. The bridge is placed between the lower set of holes and the nut is placed between the upper set of holes. Use a piece of masking tape at each end to hold the bridge and nut in place. IMPORTANT: The 4 pieces of tape will have to be removed once the keys are installed.
(SEE PHOTO #3)
Fold your 2nd copy of the Mbira Diagram along the line labelled "To Tune Keys" and slip it onto the soundboard so that it butts up against the taped-down metal bridge. Slide each key over the metal bridge, under the pressure bar and over the wooden nut. The pressure bar should be close enough to the soundboard to hold each key loosely and keep them from sliding around too much. Tighten each bolt in the pressure bar slightly to achieve this result. As you install the keys, be sure to check for even spacing and arrangement. When each key is in place and at the same length as shown on the Mbira Diagram, tighten down the pressure bar until the keys vibrate to a pitch when plucked down. DON'T OVERTIGHTEN, AS THIS WILL MAKE IT DIFFICULT TO TUNE THE KEYS. You'll probably have to adjust the tightness of the pressure bar to reach this point. It the key buzzes, it's too loose and you'll need to tighten down on the pressure bar. Remove the tape from the nut and bridge at this point.
(SEE PHOTOS #5 AND #6)
Print 2 copies of the Mbira Diagram for use when adding the keys and tuning.
Slip each of the 3 machine bolts all the way through the wooden pressure bar so that the rounded part of the dowel is facing you and the flat bottom is on the bottom. From the front of the soundboard, screw each bolt into the opening of the tee-nut. Be sure that the bolt is always flush against the top side of the pressure bar as you do this. Leave about a 5/16" space between the surface of the soundboard and the flat bottom of the pressure bar. (There is a 5/16" gauge in the upper right hand corner of the Mbira Diagram to help you.) This is done so that there is enough room to allow you to slip the keys under the pressure bar.
(SEE PHOTOS #2A AND #2B)
Working from left to right, starting with the left set of keys and then with the right set, lay each key from each set on top of the corresponding key on the Mbira Diagram to be sure that you have them in the right and final order. Leave the keys on the Diagram.
(SEE PHOTO #4)
The diagram lists the pitches for each key. The pitch of any vibrating bar goes lower as it lengthens, so shortening the vibrating length of the key will raise its pitch, and lengthening the vibrating length of the key will lower its pitch. Use the small plywood block or the flat blade of a screwdriver to push the key. You can also CAREFULLY lift the key at both ends with your fingers and push it. (The vibrating length of the key is the distance from the center of the bridge to the tip of the key where it is plucked.) When the keys are tuned and arranged to your liking, tighten the bolts on the pressure bar so that you get a clean ringing tone without buzzing. The keys should be firmly in place, but you should be able to shift them from side to side to adjust the "splay" and also move the key for fine tuning. DON'T OVERTIGHTEN. Watch the soundboard for the first few weeks to see if it is bending due to overtightening.
(SEE PHOTO #7)
mbira (photo aid)
PHOTO #1: Installing the tee-nuts.
PHOTO #2A: Mounting the pressure bar.
PHOTO #2B: 5/16" space between soundboard and pressure bar.
PHOTO #3: Placement of the bridge and nut.
PHOTO #4: Keys placed on Mbira Document.
PHOTO #5: Positioning keys on the soundboard.
PHOTO #6: Tightening the pressure bar.
PHOTO #7: Tunning the keys.