To provide an electronic keyboard musical instrument and a program that can be constituted extremely at a low cost and suitably generate a musical sound signal even when a player releases a key during a key stroke.

When V1 is larger than a prescribed sounding determination speed Vp, a predicted value V2' of V2 and a key-ON predicted time t3' when the key reaches a third contact position (3rd) are found based upon an energization limit speed (maximum speed when a hammer is not further energized) shown by a broken line in Fig. 4(d). When the key reaches the third contact position before t3', a musical sound signal is generated based upon measured V1 and V2. When the key does not reach the third contact position by t3', a musical sound signal is synthesized based upon the measured value of V1 and the predicted value V2'.