To produce any musical sound we need:
1. Something that can vibrate with a particular frequency
2. Something that can make the 1st something vibrate
3. Something that can amplify the sound produced by the 1st something with the help of the 2nd something, preferably making it pleasant to hear
That's pretty much it.
In a wind instrument the sound producing part is a mouthpiece or a reed. In a drum it is a membrane. In a singer's body it is vocal cords. In a violin, as in any other stringed instrument, this is a string set in motion with a bow. The rest of the violin increases the level of the sound made by the vibrating string and "enriches" it if it is a good instrument.
There is one little thing, without which the bow would not be able to move the string. It is rosin, also called colophony or Greek pitch, produced by heating fresh liquid resin, mostly obtained from pines. It is semi-transparent and varies in color from yellow to black. The term "colophony" comes from colophonia resina, Latin for 'resin from Colophon', a city in Ancient Greece.
Rosin is actively used in many industries, in pharmacology, in sports and in painting. And practically everywhere it is a means to achieve adhesion, viscosity and friction. In violin playing it is needed to get the required contact between the bow hair and the string.
Rosins differ in their hardness. In warm and humid environment harder rosin works better, while for dry and cool climate softer rosin is preferable. For higher pitched instruments, such as violin or viola, Chinese Erhu or Persian Kemancheh, players use hard rosin, softer for cello and very soft and sticky for double bass.
Pirastro, one of the main string makers, is also known as producer of high quality and comparatively inexpensive rosins for practically all types of bowed instruments.
Gold is one of the most popular medium hard Violin/Viola rosins:
They also make a very good rosin for students. Unlike all other Pirasto rosins, Piranito is of a rectangular shape and packed in a secure plastic box:
Pirastro's main competitor on the string market is Thomastik-Infeld. Like Pirastro, Tomastik has developed rosin models to match their own string models. Vision Violin Rosin is one of the examples:
This does not mean at all that Thomastik rosin cannot be used with Pirastro strings, and vice versa. Usually one rosin is enough for a couple of years, sometimes even more, while the strings have to be changed much more often.
For students Thomastik offers high quality cake shape Dominant Rosin in a soft cloth and round tin container that protects it from cracking.
D'Addario, an approved guitar string maker from US, also produces strings and rosins for orchestral instruments. Their Kaplan Rosin is not only great in quality, providing perfect grip and smooth contact between the bow hair and the string, it also looks amazing! It can make an excellent gift for any string player!
Kaplan rosin comes in dark and light formulae.
They don't need any more. They know that any string player would be happy to have Larsen rosin.