There are provided a mobile device that is equipped with a musical
composition-reproducing section and capable of curtailing the battery
drain as much as possible, and a mobile device that prevents the quality
of reproduced musical tones from being degraded even if the voltage level
of the battery lowers. A battery voltage detector monitors an voltage
level of a battery. The musical composition-reproducing section is
controlled such that the number of parts of the musical composition
reproduced by the musical composition-reproducing section is reduced when
the monitored voltage level of the battery becomes lower than a reference
value. In other forms of the invention, when the monitored voltage level
of the battery becomes lower than a reference value, a first
predetermined number of parts of the musical composition data are
assigned to intrinsic ones of a larger second predetermined number of
parts that correspond to the first predetermined number of parts of said
musical composition, as well as to other ones of the second predetermined
number of parts than the intrinsic ones, for reproduction of the musical
composition, or the gain of a variable-gain amplifier is increased to
compensate for the lowering of the volume of the reproduced parts.