The older Casiotone keyboards with analogue circuitry can generally be modified to accept external clock signals for synchronising their rhythms to other equipment - but there are a few caveats: 1. there are various Casiotone 'families' based on different chipsets and implementations. This means there's no standard way to do this across all models and even models that share the same CPU might be programmed differently. For example, with an external clock signal, the CT-310 and the MT-65 sync at the same tempo while the MT-86 plays at half their speed. 2. the mod outlined below might not deliver a rock solid sync - the resultant system can be prone to glitches unless buffered in some way, so making adjustments to tempo on the fly or switching other gear on and off, can cause things to go awry. 3. there are various sync signal formats in use, (12 , 24 or 48 ppqn being common), however, these do not apply to the Casiotones. With the mod below, they require multiplying