In the guild of guitarists, it is common to work with guitar synthesizers because the emulation of a great variety of sounds that are produced by different musical instruments, starting from just playing the guitar, which means, a piece of music is played with a guitar, but other musical instruments are actually heard such as, a saxophone, a violin, a piano or percussions, depending on the instrument that has been selected. The problem that arises in this article is that synthesizers are expensive and due to their size, the transportation of the equipment is often impractical. As mentioned, the development of a mobile application that has the function of a monophonic synthesizer is proposed as a solution. In this way, the cost is greatly reduced, and additionally, the user is able to install the application on a mobile device with Android operating system and connect it to an electric or electro-acoustic guitar through an audio interface; obtaining as a result, a functional technological instrument by offering guitarists an alternative with respect to conventional synthesizers. The construction of this application used the Fast Fourier Transform Radix-2 as a signal recognition algorithm, which allowed obtaining the fundamental frequencies generated by the guitar, which were transformed into MIDI notation and later used in sound emulation.