Complex sentence: In 1968 the internal bracing of the Dove was made heavier; while this made a sturdier guitar that was less likely to be returned to Gibson for warranty work, the volume of the guitar was reduced and the tone was negatively affected.
Split into simpler sentences: In 1968 the internal bracing of the Dove was made heavier. This sturdier guitar was less likely to be returned to Gibson for warranty work, but it's volume was reduced tone negatively affected.