Bontempi - Concertino 25S

Bontempi - Concertino 25S (polyphonic mini- keyboard without rhythm)

This rare Bontempi mini- keyboard is 2 note polyphonic with 3 preset sounds those include a chorus/ phasing effect. The sounds remind to C64 timbres with a cheesy howling start and end. The keyboard range can be switched by 1 octave, but the short mini keys have an odd shape (like with the Hammond Solovox tube keyboard) and are not really responsive. There is no rhythm.

main features:

25 mini- keys (white keys are wider than normal)
built-in small speaker (with unpleasant midrange resonance)
2 note polyphonic main voice
all functions selected through black keys + select button
3 preset sounds {brass, flute, fantasy}
volume control (3 steps)
octave select (2 steps, mislabelled "transposer"}
sound generator based on squarewave with vibrato and chorus effect
CPU= "IRIS X4, 27432431, B22BA BIBT, 9205" (44 pin SMD, crystal clocked)
auto power-off
no jacks

These stray discrete components belong there and were not added by me.

notes:

This instrument seems to be mechanically a variant of the hardware family of Bontempi B5, B20 and B40., while the preset sounds have a chorus effect like Bontempi ET 202. An unusual detail on the box writing is the claim "safe and hygienic", which apparently alludes to that this keyboard was designed to compete with those mouthpiece operated school melodicas; I still remember my nightmares of those loudly tooting Hohner snot boxes, those as a kid I found so disgusting that I refused to participate in the school musics lessons until my mother bought me a Casio VL-Tone 1. The Bontempi Concertino 25S seems to be very rare; at least on eBay I never saw another specimen yet. Unfortunately there is nowhere a hint when it was made.

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 BK32.

*removal of these screws voids warranty...*

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