digibell envelope shaper

This circuit is intended to improve the sound of the `Digibell`, which was published in Elektor No 14(June 1976). The tones produced by the original Digibell circuit, which is reproduced in igure 1, terminate abruptly at the end of each note in the sequence. The simple envelope shaper described here causes the notes to die away exponen- tially, which is much m