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Two new pelog sarons added in 2003 to play Babar Layar and the pelog peking that was replaced in 1987 needed retuning very badly. The sarons were out of tune by a quarter to a third of a note (10-20 Hz). This is a well-known problem after the first few years. The theory behind lowering the pitch back is also well-known: remove some material from the underside at the middle of the bars. A little frequency analyser was installed on the laptop to gauge progress, and we started.
The first try was with a small conical grinder, pictured on the right. Afraid to go too fast, we were surprised the pitch went down only a little. With a lot of effort the pitch came down 1 Hz; 14 Hz to go. Another circular grinder (left) looked more promising at first: 3 Hz down in one go. However, two of these appeared to be due to the heat; when the bar was cooled down we had again only gained one small Hertz. After more than half an hour of work we had only reached the half-way mark, 600 Hz.
Time for a tougher grindstone (right). The marks this one made on the apparently very tough bronze were identical to the ones the instrument maker had made to tune it in the first place, which gave some confidence. Now, it "only" took half an hour per bar to go down 10 Hz, mainly because the engine was too weak and could not support continuous grinding. So, after tuning the two "1"s, we stopped, had lunch and agreed to continue after renting more powerful tools.
Preliminary conclusion: the theory works, but you need good tools to tune a saron a long way. Stay tuned for the next episode...
The best we could find was to attach a Piranha grinding disc to a drill. This set-up nallowed us to tune a bar to the rough vicinity of where it should be in about 20 minutes. We cooled the bars to room temperature in a bucket of water. The six remaining bars of two sarons took two hours of solid work, using up hree grinding discs. Afterward we tuned them to the last Hertz equal to the old museum saron.
Even the teacher agreed the sound was much better than before.
The peking player likes the pitch, but complains that the edge is rougher when damping, and the brilliance of the 5 has diminished somewhat. We are not expert enough to restore that.
In conclusion: yes, amateurs can tune saron keys without risking too much. It is a lot more more work than we anticipated, and you need good tools: bronze is tough. Make sure you measure the frequency at the same temperature: cool the bar after grinding.
