Musical instruments are complex multimodal interfaces combining audiovisual information and motivating researchers to design intuitive and creative ways of communication between the user and the digital system. We demonstrated a musical interface based on an optical fiber specklegram sensor (FSS) for one octave of C major scale. The setup comprises a laser source and a camera connected by a multimode optical fiber cable with foam pads marking the notes. The software recovers the pressed key by computing the cross-correlation coefficient between the immediate speckle pattern and the reference images from prior calibration, estimating their similarity, and taking the closest option as the output. Simultaneously, the software plays the identified key with a sound synthesizer. The experiments validated the proposed interface to play the calibrated notes, independent of the input sequence, with a response delay within 0.5 s, for a single fiber cable and further discuss the possibility of playing chords. With the musical interface processing the positional information of external stimuli, it simplifies the hardware configuration and allows different techniques of musical expression.