The process of learning to play a string instrument is a notoriously difficult task. A new student to the instrument is faced with mastering multiple, interconnected physical movements in order to become a skillful player. In their development, one measure of a players quality is their tone, which is the result of the combination of the physical characteristics of the instrument and their technique in playing it. This paper describes preliminary research into creating an intuitive, real-time device for evaluating the quality of tone generation on the cello: a “timbre-tuner” to aid cellists evaluate their tone quality. Data for the study was collected from six post-secondary music students, consisting of recordings of scales covering the entire range of the cello. Comprehensive spectral audio analysis was performed on the data set in order to evaluate features suitable to describe tone quality. An inverse relationship was found between the harmonic centroid and pitch played, which became more pronounced when restricted to the A string. In addition, a model for predicting the harmonic centroid at different pitches on the A string was created. Results from informal listening tests support the use of the harmonic centroid as an appropriate measure for tone quality.