“Shamisen” is not one instrument. The three families are separated by the thickness of the neck (sao), and the difference between them is about 2.4 millimetres in total — small enough that photographs are useless, decisive enough that the wrong one cannot play your genre properly.
The three necks, measured
The measurement is taken below the chibukuro — the narrow upper part of the neck.
| Type | Neck width | Genres |
|---|---|---|
| Hosozao (thin) | 8 bu 4 rin — about 25.4 mm | Nagauta, kouta, hauta |
| Chuzao (medium) | 8 bu 8 rin — about 26.6 mm | Hauta, kouta, jiuta, minyo |
| Futozao (thick) | 9 bu 2 rin — about 27.8 mm | Tsugaru, gidayu |
Each step is roughly 1.2 mm. That is why you cannot identify a shamisen type from a listing photo, and why “shamisen, good condition” tells a buyer almost nothing.
Sound follows the neck — and the body
Futozao plays loud, with depth and weight. Hosozao is lighter and brighter. The neck is the label, but the body size and other fittings move with it.
The detail that surprises people: two futozao instruments — one for gidayu, one for Tsugaru — sound completely different from each other. The neck width is the same. What differs is how the skin is stretched, and the koma (bridge) and bachi used. So “futozao” narrows the search; it does not finish it.
The convention is a convention
These pairings are the standard, not a rule of physics. Players do deviate, by preference or in pursuit of a particular sound. If your teacher specifies something outside the table, the teacher is right — they are choosing the sound, and the table is only describing what is usual.
What to settle, in order
- Genre — decides the neck. Everything else is downstream.
- Neck width — and for a used instrument, ask the seller to measure below the chibukuro rather than trusting the description.
- Skin, koma, bachi — these are what separate two instruments of the same neck width. See Shamisen Skin and Choosing a Bachi.
- Strings — the set is chosen by genre. See Shamisen String Numbers.
For the medium-neck case specifically, see Minyo (Folk) Shamisen. For the anatomy of the instrument, The Parts of the Shamisen.
Sources. Neck widths in bu/rin and millimetres, the measuring point below the chibukuro, the genre assignments, and the note that players deviate from convention: Mukouyama (mukouyama.jp). The gidayu/Tsugaru distinction arising from skin tension, koma and bachi: wa-gokoro.jp. Checked 2026-08-18. We do not sell instruments — confirm measurements with the seller or maker.