See the attached schematic. Not pretty, but it should work.
Values will depend on your circumstances (Number of LEDS, voltage of audio signal, cross-over frequencies, gate current of chosen SCR). It doesn't have to be exact.
As an example, if your audio is around 10V and the gate current of the SCRs is 5ma then choose R13, R14 and R15 to be 2K each. If we want the cross-over frequencies to be around 500Hz and 5KHz then:
C1 and C4 = 1/(2000 * 500) = 1uF
C2 and C3 = 1/(2000 * 5000) = 0.1uF
