You may have seen the shruti box before – this briefcase-sized instrument has been making the rounds and finding its way into all sorts of musical genres. Despite its rather mundane and unassuming appearance, the shruti box (sometimes called surpeti) can create spellbinding sounds, providing a beautiful drone to sit beneath a song or other melody. This instrument's harmonious and soothing qualities make it a perfect tool for music therapy, and the intuitive and simple key layout make it an excellent device for musical education, as well as musical recreation for people of all ages.
In more technical terms, the shruti box is a bellows-driven portable free-reed wind instrument. Different shruti boxes come equipped with different sets of keys. Some are single-octave chromatic key layouts (from low C to high C, with a layout much like a piano keyboard) while others might be diatonic (set for the key of D and its relative modes, for example). Higher-pitched shruti are said to be "female" while those pitched an octave or so lower are often called "male" shruti. The name shruti is derived from śruti [ɕrʊtɪ], or the smallest pitch interval that the human ear can detect or an instrument can produce, a concept that can be found in ancient Sanskrit texts.
When playing the instrument, it's common to have the shruti box either sitting on the floor in front of the musician (who has their hand resting on the bellows, or who might choose to control the bellows via foot pedal), or on the lap. Generally for a drone, a musician will select two notes that are either a third or a fifth apart, chromatically (For example, C and E would be a third apart, while C and G would be a fifth apart). For this reason, knowledge of music theory can prove quite useful in getting oriented on the instrument. That said, it is fairly intuitive, and requires a certain amount of trial and error to find what is most pleasing to the ear.
The shruti free reeds are metal (typically steel or brass) and air is pushed through these reeds when their corresponding holes are uncovered, using the force of gravity. One hand will pull air into the bellows, which causes the front keyboard to lift, and create sound as it gradually falls and air escapes through the open sound holes. Doing a longer or faster pull on the bellows will create a louder drone, while shorter and slower pulls will create a softer drone. Being able to adjust the volume can also allow the musician to add pulse and rhythm to the music by pulling on the bellows to create a swelling sound on the emphasized beat or phrase in the music.
A backing drone can prove useful for tuning the voice, learning the basics of harmony, creating a relaxing mood, and also providing a backdrop for storytelling or spoken word poetry. There aren't many instruments out there which can create such beautiful sounds and which can be played with only one hand (or completely hands-free, with the addition of a foot pedal), while allowing the musician to simultaneously sing or play another one-handed instrument. The shruti box is special in that respect.
The shruti has its origins in India, and is a descendant of the Chinese sheng along with other free-reed instruments including harmonica, accordion and concertina. Notably, the sheng provided inspiration for the European harmonium, which then made its way to India. The shruti box then evolved from the practice of placing a stop on a key of the harmonium in order to create a drone, and is a simpler and more portable instrument than harmonium. Perhaps because of its ease of use and portability, it has become increasingly popular in folk music circles. In the 1990's, Nóirín Ní Riain brought it to Ireland, where it still has a place in Irish song tradition. Where will it travel to next?