The petosa Concert Series "Cathedral" converter models are completely handmade of the finest quality materials and craftsmanship available anywhere in the world today. A custom built Cathedral models take 18 months to make.

A Converter system allows the left-hand of the accordion to switch (convert) between the normal Stradella (chord note) system & a chromatic Free-Bass (single note) system as in a standard right hand 4 row chromatic accordion. The Free-Bass uses 4 rows of chromatic scale buttons with a 58 note range (low E - B3) using up to 3 sets of reeds and 7 registers.

The special patented "Converter" system is completely handmade of hard steel to maintain each of the several hundred intricate pieces assembled and adjusted to precise tolerances.

TREBLE SIDE.... Bassoon and Clarinet reeds are mounted in petosa's special wood "Tone Chamber" made of a single milled piece of solid aged mahogany for the ultimate in sound quality. A second middle reed and piccolo reed are outside the chamber and all reeds dry tuned in perfect unison at A-440. In the Cathedral Piano model an additional unique piccolo reed is added called the "quint". This reed is tuned a perfect 5th above the normal piccolo reed to give a true pipe organ type sound.

FREE-BASS.... 58 notes (E - cis3), 3 sets of "petosa" handmade reeds pitched to 8 + 8 + 2 or some may refer to as 16 + 16 + 4. Four rows of chromatic buttons. The lowest note "E" gives a deep true organ pedal tone. A special octave switch producing a double octave note on the first octave range of the Free Bass System, (low E - D). Available in standard "C"
griff or standard "B" Russian griff.

PIANO Keyboard.... consists of 45 notes, (e -c4) Completely handmade keyboard of aged solid American walnut and hand cut lucite key tops. Five sets of genuine "petosa" handmade reeds 16 + 8 + 8 + 4 +4v, Bassoon & Clarinet in "petosa" tone chamber, Flute & Piccolo out of chamber and 2nd piccolo quint "v" tuned a 5th above the standard Piccolo.

BAYAN Keyboard.... 64 notes, (E-g4). Five row chromatic "C" (Italian/Swedish griff) or B" (Russian/Norweign) griff. Four sets of genuine "petosa" handmade reeds: 16 + 8 + 8 + 4, Bassoon & Clarinet in "petosa" tone chamber, Flute & Piccolo out of chamber.