While a full orchestra consists of >70 musicians with each playing one or more instruments, chamber music features only 3 to 5 instruments. The motivation behind this study was to understand why the violin, viola, and cello became the most popular combination of chamber music among >70 instruments, and to analyze this phenomenon from both a physics and acoustics perspective. Octave frequency analysis revealed that each instrument possesses a dominant fundamental frequency, while its overtones (double or triple the frequency) exist at a lower intensity. These instruments perfectly align their fundamental octaves with each other's overtones, enhancing their collective harmony. For an ensemble to be a viable choice for chamber music, the sounds frequencies generated from each instruments' open strings should cover the primary octave frequencies seamlessly. The violin, viola, and cello meet this criterion better than the violin, viola, and double bass. Although it is only limited to the open string case, the spectral gap in the violin, viola, and double bass and the weak overtone overlap serves as the reasons why this combination is rarely seen as a standard chamber ensemble. However, adding a cello to create a four-instrument combination (violin, viola, cello, and double bass) eliminates this gap and creates more resonant overtone overlay while expanding the overall pitch range. Furthermore, the ensemble's seating arrangement was analyzed based on two factors, including the convergence of sound projection from the instruments and the musicians' lines of sight for eye contact.