Thumb Piano (pentatonic key of C)
Instrument type: ideophone
Solid wood block 130 x 90mm, hardwood dowel 12 x 90mm, 2 wire knitting needles size 11 or 12 (tines), 2 different sized plastic knitting needles, 2 machine screws 30mm 8 gauge, good PVA or super glue
Tools small hack saw, mitre saw, hammer, 100 grit sandpaper, file, ruler, drill/bits, screw driver, pliers, pencil, electric tuner or good ear
1 Saw lengths of knitting needles to 125, 120, 110, 105, 100, 95mm. Smooth cut ends with sandpaper and flatten one end with a hammer.
2 Saw wood block, hardwood dowel and plastic knitting needles to size, sand smooth. Sand a flat strip 2mm wide along length of plastic needles.
3 Drill holes in hardwood dowel at place shown on plans (15mm from each end), they should be large enough for the screw to slide through.
4 Using hardwood dowel as a guide, drill smaller holes into the wood block so that screws will be strongly anchored.
5 Glue the flat strip of the plastic needles onto the wood block at places shown on the plan. Note the larger needle goes at the 40mm mark. Use strong PVA or super glue.
6 Screw the hardwood dowel into the woodblock far enough so that the wire tines can be pushed underneath.
7 Insert wire tines in order of length under hardwood dowel but over plastic needles.
8 Screw dowel down so that wire tines are held in place but still able to be moved with fingers.
9 Starting with the low C tine, test the pitch with a electronic tuner or tuned instrument. If the pitch is too high, using pliers, make the tine longer by sliding the tine 1mm at a time until the note C is made. Repeat tuning process for other tines.
10 Give the screws one last tighten to lock tines in place. Tighten further if there is a buzzing in the sound of any notes.
• Mark the tuned positions of the tines with a scratch above where the tine rests on the large plastic needle.
• Make small grooves in the large plastic needle so that tines cannot slide sideways.
• The lengths given for tines may be too long or short depending on the wire knitting needle you use. Some experimenting may need to be done. Other wire or a different material can also be used for the tines. Such as bicycle spokes, stainless welding rod or bamboo strips . Anything with sufficient springiness to drive a vibration in the sound board. To make a pentatonic C tuning with different tine materials, the lengths will be different from those given in the plan. Wire knitting needles are easy to find and a soft enough metal for children to work with safely.
• The arrangement of the notes and scale can also be changed. African kalimbas are often arranged with the deepest notes in the middle of the instrument.
• The type and size of wood used for the block will also make a difference to the tone of the instrument. Experiment with a resonating chamber for more sustain.