Can not get more than 3 timers to work on Mega2560

Hi,
Does anyone know how to get 6 timers to work on Mega2560 so I can play six tones at once?

OK.. Iv'e figured out how to make it work now...
in the "Tone.CPP" file change all lines with

#if defined(AVR_ATmega1280)
to
#if defined(AVR_ATmega1280)||(AVR_ATmega2560)