Trill is a type of musical ornament. In automatic playback of piano music scores, trills are usually synthesised as a sequence of repeated notes with equal duration and dynamic level. This is not how trills are performed by pianists. In this study, trills were performed by three pianists on a Yamaha Disklavier and recorded as both audio and MIDI files. Then note duration, inter-onset interval (IOI) and key velocity for each note were extracted from MIDI files and analyzed in relation to hands, notes and emotions. Four significant effects were found; 1) hand effect: trills on right hand were in average performed with a faster rate, shorter note duration, longer off duration and faster key velocity, 2) finger effect: within the two notes forming a trill, notes with lower fingering number were performed with shorter off duration, while keeping note duration and key velocity close, 3) emotion effect: emotion mainly contributed to dynamic level, 4) crescendo effect: when crescendo happened, note duration and off duration compensated with each other and kept IOI at a almost constant value.