This thesis describes mechanical improvements made to the bassoon and how they influenced solo compositions for the instrument in the 17th and 18th centuries. By focusing on bassoon concertos by three leading composers, the study provides a deeper understanding of the idiomatic perceptions and tendencies that characterized the approaches to the bassoon as an instrument with distinctive tone color, and to the concerto as a preferred genre in the Baroque, Galant, and Classical style eras. The concertos analyzed are Antonio Vivaldi's Concerto for Bassoon in Bb Major, RV 503, Johann Christian Bach's Concerto for Bassoon and Orchestra in Bb Major, and the Concerto for Bassoon K191 by Wolfgang Amadeus Mozart. Each concerto has three movements in what had become the standard fast-slow-fast format for the genre. All three concertos are in Bb Major, allowing comparisons of range, interval preference, and melodic material, among other features. The three concertos retain elements of “ritornello” procedure, initiated by earlier composers, notably Torelli. While these commonalities will be discussed, our emphasis is primarily on the structure of the instruments used by the composers. The bassoon Vivaldi knew was likely a four-keyed instrument. This instrument will be described then compared to the bassoons in use at the time of J.C. Bach and Mozart. Citing treatises and other sources published prior and contemporary with these concertos, developments in the bassoon's design will be noted and related to features in the concertos that reflect the developments. Especially important to the following study has been Simon McVeigh and Jehoash Hirshberg’s The Italian Solo Concerto. Analyses are based upon scores in the collected editions, and Akos Fodor's edition of the J.C. Bach Concerto . My analysis follows the methodology outlined by William Marvin’s introduction to writing musical analytical essays and Richard J. Wingell's Writing About Music: An Introductory Guide. Donald Francis Tovey's Essays in Musical Analysis has been especially helpful in formulating descriptions of harmonic and melodic language, the keys and scales used to create the solo lines, modulations, temporal organizations, phrase structures, range, chromaticism, ornamentation, and idiomatic characteristics. My approach to the thesis has been both as an active bassoonist-performer and as a music historian. Throughout, I have attempted to remain objective, thorough, and accurate.