Stone-age Music: Slate Marimba

What is the world’s oldest musical instrument?  Scientists have found bone flutes that are thousands of years old.  Well what about stone instruments?  Hit two rocks together and you’ll certainly get some sort of sound.

I decided to make an instrument out of rock.  Here’s my “Stone Marimba” made using slate slabs.  Slate is a fine-grained metamorphic rock that can easily be split into smooth, flat pieces.  I saw one of these strange instruments and decided to make one.  Here it is, and here’s how I did it.

Here are 3 types of slate

Here are 3 types of slate

Here are three types of slate.  I found used slate roofing tiles.  Nice and thin, so that it would cut easier and sound good as a marimba bar.

Ready to cut the stone

Ready to cut the stone

I wore a full face mask, hearing protection and a respirator.

Chuck cuts the slate

Chuck cuts the slate

I found an old funky table saw and used a masonry blade (made to cut tile and stone).  Regular masonry saws usually have running water on the blade, but since I didn’t it threw up a lot of dust..and was very noisy.

Work Bench for project

Work Bench for project

I used this temporary bench to do the work.

Using a small digital tuner to check the pitch of the bar.

Using a small digital tuner to check the pitch of the bar.

I cut the bars to the same width (3.5 inches) and tuned them to length.  I checked the tuning with this small digital tuner.  If the bar is too low in pitch just cut the end of the bar or sand it.  If the pitch is too high you can glue small pieces at the end to lower the pitch.

Finding the nodes with salt

Finding the nodes with salt

Next I made two small block stands with fishing string.  I suspended the bar on the strings and poured salt on each end.  Tapping the bar with a mallet makes the salt move to the “node points”.  This is a point on the bar with the least vibration and a perfect place to suspend it for the best sound.  I marked the node points.

Drilling the bar

Drilling the bar

I used a masonry drill and drilled a whole at each end along the nodal points.  These holes are for the little pegs to hold the bar in place.

Weather stripping placed on nodes

Weather stripping placed on nodes

Next I attached weather stripping on each end along the axis of the node points.

Wooden frame for the stone marimba

Wooden frame for the stone marimba

The next step is to make the wood frame on which to mount the bars.  I made the frame so that it fit the node points from the longest to the shortest slate bar.

Mounted stone bars

Mounted stone bars

Here’s how the bars look mounted.  I put vinyl lettering to designate the pitches.

Finished Stone Marimba

Finished Stone Marimba

Here’s the finished Stone marimba.  It is one and a half octaves long.  I’m working on another octave lower and will also make higher pitches for a full range.

Here’s what it sounds like: