Abstract
The military bands of the government of Costa Rica played a leading and outstanding role in the musical development of the nation. The investigative works on the evolution and progress of the Costa Rican music have had to contemplate sections on the history of those musical groups. The directors and older musicians had to keep a strict control over the work done; For that purpose, they filled official logs with information on the repertoire executed, the personnel management and punishments, asset inventories and the file of scores. These logs are unknown primary sources that must be available, to carry out investigations which provide relevant historical data. Thus, for example, thanks to them, the present work will be able to establish a historiographic base with the purpose of reconstructing a referential historical framework on the importance of the Military Band of Alajuela as diffuser of national music.