The short answer: the first string is thickest and lowest, the third thinnest and highest
The difference between the shamisen’s first, second, and third strings comes down to thickness and pitch. The ichi-no-ito (first) is the thickest and lowest, the san-no-ito (third) is the thinnest and highest, and the ni-no-ito (second) sits in between. Thicker strings sound lower, thinner ones higher — grasp this and both string choice and tuning make sense.
The three strings, in order
Counting from the thick side of the neck: the ichi-no-ito (thickest, the low-end foundation), the ni-no-ito (medium, the mid-range), and the san-no-ito (thinnest, the high notes and melody). In tuning, you set the first string as the reference and set the others relative to it, so understanding the three strings’ relationship is central to tuning too.
| String | Thickness | Pitch | Role |
|---|---|---|---|
| Ichi-no-ito | Thickest | Low | Low-end foundation |
| Ni-no-ito | Medium | Mid | Mid-range |
| San-no-ito | Thinnest | High | High notes / melody |
Why thicker means lower
As with all string instruments, a thicker (heavier) string vibrates more slowly and sounds lower; a thinner (lighter) one vibrates faster and sounds higher. Choosing string thickness (the gauge, go) is therefore choosing the balance of pitch and tone: thick for a strong low sound, thin for a light high one.
Choosing the gauge for each string
Gauge is a number — larger is thicker. Use a heavier gauge for the first string, a lighter one for the third, and a middle gauge for the second, keeping the three in balanced order. The exact numbers depend on genre: the thick-necked Tsugaru runs heavier overall, the thin-necked Nagauta lighter.
Each string wears at a different rate
The thin third string breaks most often and is replaced most frequently, because thinner strings are more affected by tension and friction; the thick first string lasts longer. Keep more spares of the third string and fewer of the first and second.
A common mistake
The usual beginner error is throwing off the order by fitting one string of the wrong gauge — e.g. replacing a broken third string with whatever is on hand. Keep the order and spacing of thicknesses consistent (thick first, thin third, medium second), whether the whole set runs heavy (Tsugaru) or light (Nagauta). Note the gauge you use so you can reproduce the same balance next time.
Restringing
Replace strings one at a time, not all at once — removing all three releases the tension suddenly and the bridge can fall or lose its position. Changing one keeps the others under tension and the balance intact.