The instrument
The CP 70 and CP 80, Yamaha's two electric grand pianos, came onto the market in 1976, the CP 70B variant in 1978. These large instruments, which at around 130 - 150 kg were still transportable, were designed for pop and rock keyboardists who appreciated the combination of conventional grand piano technology with electric amplification. The manual of the CP 70 is equipped with 73 keys, that of the CP 80 with 88 keys.
Details
Electromechanical devices from Wurlitzer and Rhodes work with pickups; bars or reeds are struck and set in vibration. Although they can be used for concerts, their sound aesthetics do not correspond to those of a piano. This is the case with the CP grand pianos from Yamaha. The sound box and the keyboard are installed in two separate boxes. The lower box is used for the keyboard and the hammer action. The upper box contains the strung harp and the damping mechanism. Special strings were developed for the strings in order to create a special sound character. For the bass, one string is strung on each of the first 15 keys, and two strings are used for the other keys, whereas a conventional piano usually has three strings. A separate piezo pickup was installed for each key for microphone transmission. The signal is amplified internally after the pickups and fed through a sound control system with controls for boosting or cutting bass, mid and treble frequencies. A tremolo can be switched on. In the Yamaha CP-70B, the tuning has been improved compared to the CP-70.