Difficulty recreating traditional FM waveforms

Sine,

1) An oscilloscope is not as useful with FM as it is with subtractive synthesis. A spectrum analyzer is more useful with FM. The reason is the common shapes of subtractive synthesis (saw, square, triangle) depend on phase relationships among the partials of a tone. But these phase relationships are not in general the same with FM. Also, they do not in general make an audible difference. The tone (of a steady tone) is basically the partial frequencies and amplitudes, not phases.

2) Take a look a the Player (NI, not user) / Blocks Base / Racks / Tutorial / Frequency Modulation.nksr . This is a simple two oscillator FM setup as close as possible to DX7 (using only two operators). Note that the oscillator on the right (the carrier) has "LIN TZ" under "FM" on the left side of the module. This is critical for acting like DX7 FM.

3) I fairly sure the Bento Box Oscillator does FM, not PM. This does not matter much for a simple two oscillator synth. The DX does PM for the sake of cascaded modulators and feedback.

drb

fm produces harmonics, no one really cares what the wave form ends up looking like. dx7's never used subtractive synthesis.

Basically any waveform is made up of sine waves if the frequency spectrum. Theoretically you can add sine waves with the proper amplitude and phase relationship and replicate any wave form. It's pretty interesting how an oscilloscope shows a picture of the wave form and a spectrum analyzer shows the amplitudes of the sine waves that make up the wave form. Have fun learning.

You 'de get a lot closer to phase modualtion FM if you set it to linear FM , but bento FM does NOT do phase modulation

Also , to get a perfectly straight saw or square on yamaha fm synths , some feedback on the modulator is required

Here's anexample using the wonderfull plogue ops7 .

And if you phase shift the modulator with 90degrees you get triangle waves (same harmonics as square ) , too lazy to fire up my tg77 :)