|These stray discrete components belong there and were not added by me.|
The "brass" preset sound resembles rather a violin with 6Hz vibrato and percussive attack phase and a tiny bit of sustain. "flute" is a flute or clarinet sound with mild chorus effect and mild vibrato; the bass range resembles a wooden pipe organ rank. "fantasy" is a squawky woodwind timbre with percussive attack, that resembles bagpipes and includes a phasing effect that cycles thinner and fuller with about 0.5Hz. The pitch of all 3 preset sounds howls up a bit during attack, and down a bit after key release, which gives the sounds a special cheesy appeal. I am not sure if this is a software feature or caused by battery voltage changes, not least since the crystal clocked CPU theoretically should prevent this; Bontempi even advertised this thing to stay always in tune.
Unusual is also the polyphonic keyboard scanning algorithm, which always plays on the 1st channel the leftmost pressed key and on the 2nd channel the rightmost pressed key, while it ignores all keys in between. This behaviour is normally only known from historical analogue synthesizers without digital CPU. The keyboard also has no matrix but connects all key contacts to the same line, thus possibly the single main IC contains a much older, semi- analogue hardware design with a couple of additional flipflops instead of a genuine software controlled digital CPU, and also the howling tones may have to do with this. (Another small keyboard with bizarre keyboard scanning technology is the Ramasio 892.)
A direct successor of this instrument was the Bontempi
Concertino 32S (with 32 midsize keys, 8 preset sounds, metronome).
Another (older) Bontempi mini keyboard with roughly similar features
like the 25S was the Bontempi Basic
|removal of these screws voids warranty...|