Being keen on FM synthesis I was keen to work out all of the permutations of oscillators for the Prophet 12, but the same patterns work for AM and presumably Sync.

The first thing to consider is the position for the Sub Octave (attached to oscillator 1). In a chain of connected oscillators with different frequencies choose the frequency you want for the Sub Octave, and make the oscillator at that frequency your Oscillator 1, then fit the chain of connected oscillators around that.

Because of the Sub Octave I am referring to my oscillators as D,C,B and A instead of 4,3,2 and 1, so if you want the Sub Octave on C then C is oscillator 1.

If you assign as many modulations as possible from the oscillator select buttons you will save on using up slots in the Mod Matrix - If B modulates A, and B is the desired Sub Octave then B is oscillator 1 and A should be Oscillator 4 to save using a Mod Matrix slot.

I can’t post diagrams so I am using B>A for B modulates A. It is possible to create loops, for example B>A, C>A,C>B. in this example C modulates A both directly and indirectly via B but factors such as wave shape and slop can cause C to have two different influences on A.

Here is the full set of ‘Algorithms’ possible for a voice on the P12

B>A. (Output A,- C and D free)

C>B,C>A. (Output A and B,- D is free)

C>A,B>A. (Output A ,- D is free)

C>B,B>A. (Output A ,- D is free)

D>C,B>A. (Output C and A )

C>B,C>A,B>A. (Output A ,- D is free) (has 1 loop)

D>B,D>A,C>A. (Output A and B)

D>C,D>B,C>A. (Output A and B)

D>A,C>A,B>A. (Output A)

D>C,D>B,D>A. (Output A,B and C)

D>C,C>A,B>A. (Output A)

D>C,C>B,C>A. (Output A and B)

D>B,C>B,B>A. (Output A)

D>C,C>B,B>A. (Output A)

D>B,D>A,C>A. (Output A and B)

D>C,D>B,C>A,B>A. (Output A)

D>B,D>A,C>B,C>A. (Output A and B)

D>C,D>A,C>B,C>A. (Output A and B) (has 1 loop)

D>C,C>B,C>A,B>A. (Output A) (has 1 loop)

D>B,D>A,C>B,B>A. (Output A) (has 1 loop)

D>C,D>B,C>B,B>A. (Output A) (has 1 loop)

D>C,D>B,C>B,C>A. (Output A and B) (has 1 loop)

D>C,D>B,D>A,C>A. (Output A and B) (has 1 loop)

D>C,D>B,D>A,C>B,C>A. (Output A and B) (has 2 loops)

D>C,D>B,D>A,C>A,B>A. (Output A) (has 2 loops)

D>B,D>A,C>B,C>A,B>A. (Output A) (has 2 loops)

D>C,D>B,D>A,C>B,B>A. (Output A) (has 3 loops)

D>C,D>A,C>B,C>A,B>A. (Output A) (has 3 loops)

D>C,D>B,C>B,C>A,B>A. (Output A) (has 3 loops)

D>C,D>B,D>A,C>B,C>A,B>A, (Output A) (has 4 loops)

It’s great to just mess with the P12 and come up with great sounds, but for FM synthesis the structure of oscillator interaction defines the possible sounds - probably why Yamaha printed the Algorithms on the top of the DX7 (they only used some of the 6 operator combinations for their 32 Algorithms but I have listed all the possible patterns for 4 oscillators here).