The bayan (Russian: бая́н, IPA: [bɐˈjæn]) is a type of chromatic button accordion developed in Russia in the early 20th century and named after the 11th-century bard Boyan.
Chromatic button system (type B), usually called Moscow system
, most Russian bayans have this system
"West European", chromatic button system (type C)
The bayan differs from western chromatic button accordions in some details of construction:
- Reeds are broader and rectangular (rather than trapezoidal).
- Reeds are often attached in large groups to a common plate (rather than in pairs); the plates are screwed to the reed block (rather than attached with wax).
- The melody-side keyboard is attached near the middle of the body (rather than at the rear).
- Reeds are generally not tuned with tremolo.
- Register switches may be operated with the chin on some larger models. (also possible with some larger European button accordions)
- The diminished seventh chord row is shifted, so that the diminished seventh G chord is where one would expect the diminished seventh C chord in the Stradella bass system.
- Converter switches that go from standard preset chords to free bass (individual bass notes) are common on the larger instruments.
- Newer instruments may feature a register where every tone played actually produces a perfect fifth.
The differences in internal construction give the bayan a different tone color from Western instruments, and the bass has a much fuller sound. Because of their range and purity of tone, bayans are often the instrument of choice for accordion virtuosi who perform classical and contemporary classical music. Two Soviet composers of note who wrote compositions for bayan are Vladislav Zolotaryov and Sofia Gubaidulina. Russian Bayan virtuoso Stas Venglevski has premiered contemporary works by Yehuda Yannay, Anthony Galla-Rini and William Susman. 
- Cherkasky, L. - Ukrainski narodni muzychni instrumenty // Tekhnika, Kiev, Ukraine, 2003 - 262 pages. ISBN 978-966-575-111-3