People have gone to great trouble and expense in the quest to make their acoustic guitar sound as good as possible. For example, installing a new saddle of one substance or another can be a good way to increase or alter certain tonal properties for the better. But that can cost a lot of money and requires a good deal of work. An easier, more affordable way to achieve a similar effect is to simply change the bridge pins from their typical plastic or wood to a harder, organic substance. By far the most popular variety is bridge pins made from polished bone. The bone pins at Maury's Music are a fine example. They cost far less than pins of more exotic materials but offer classic looks and a noticeable increase in sound quality.
The chief point of sound wave transfer between the played strings and the top and tone woods of the guitar is the bridge. But it is the saddle and bridge pins which conduct the string vibration to the bridge itself. The bridge plate under the top likewise receives vibration from the pins and the bridge. Those vibrations are filtered through the material of the saddle and pins, with certain frequencies coming through clearly and others being muted. Therefore the pins and saddle have a great deal to do with the guitar's tonal properties and how well notes sustain at a given pitch.
Most guitars are sold with plastic pins because they are cheap and also inert, which means they will not expand and possibly crack the bridge if exposed to extreme changes in temperature and humidity during shipping. But they are relatively poor conductors of tonal vibration and do little in the way of helping the guitar sound good. Pins made out of wood like ebony or rosewood can look great but can result in a voice with less noticeable overtones in the highest reaches of the treble. This can be a good thing if the guitar sounds with a brash or shrill quality. In other words, wooden pins mellow out bright guitars. But they can also swell up when humidity increases making them too tight in the pin slots.
Bone pins are not affected by environmental changes but they will improve the clarity of the voice, the purity of the trebles and increase sustain when compared to plastic or wooden pins. Other advantages to switching out the bridge pins include the fact it requires no surgery the way saddle replacement can. This is noteworthy for owners of vintage instruments or replicas that still have a glued-in, long saddle. But even in guitars with short saddles made of plastic or Micarta the addition of bone bridge pins can make a very welcome difference at a very small cost.
I put my new bone pins in a Martin 00-15 which features a mahogany top and comes with plastic pins. There was an instant increase in volume and sustain and the definition of this otherwise sweet and mellow guitar was also increased nicely. When I exchanged bone and wood in my Brazilian rosewood, Adirondack spruce OMC-28B there was even more change to notice. This may be due to the fact it is such a resonant guitar and also because it has a fossilized walrus ivory saddle. The wooden pins softened the edge of the trebles and warmed up the overall voice; but the guitar lost a great deal of its harmonic glimmer. The bone pins increased that ring off the top voice and added a great deal of focused singing up in the higher registers and harmonics. These same pins in my friend's OM size Ibanez likewise improved the volume, tone and sustain in a pleasing manner. They seem to increase the purity of the fundamental notes as well, which can help out less expensive guitars with bolt-on necks.
Now, it is fair to say the material of the saddle affects the tone of a guitar considerably; bridge pins not so much. This is not a bad thing. The fact that switching the pins results in a more subtle change also allows one to tweak the voice of guitar more precisely. This is why some musicians like the saddle and pins to be of the same substance and others prefer them to be of different but complimentary materials. Bridge pins can also be exchanged easily and one can even mix various kinds of bridge pins, string by string, if they want to go for micromanaging their guitar's tonal output.
I find that bone pins are a minor expense at most and can add just the right amount of clarity and ring. Without having to know the ins and outs of guitar technology any player can install a set of polished bone bridge pins and instantly improve the sound of their instrument, whether it is a $500 student model or a professional level guitar costing tens times as much.
Out of a possible 8 Notes on the T Spoon Scale of Guitaracity I give these bone bridge pins a sustained 6 Notes.