This paper proposes a musical performance feedback system based on real-time audio-score alignment for musical instrument education of beginner musicians. In the proposed system, we do not make use of symbolic data such as MIDI, but acquire a real-time audio input from on-board microphone of smartphone. Then, the system finds onset and pitch of the note from the signal, to align this information with the ground truth musical score. Real-time alignment allows the system to evaluate whether the user played the correct note or not, regardless of its timing, which enables user to play at their own speed, as playing same tempo with original musical score is problematic for beginners. As an output of evaluation, the system notifies the user about which part they are currently performing, and which note were played incorrectly.