Tremolo, vibrato, a.m. and f.m? Closely related actually, despite the former two being associated with pressure (sound) waves and the latter two with electro-magnetic (radio) waves.
Place your mouse cursor here and listen to the tone. It has a constant frequency of 700Hz, a constant level and can be represented graphically, such as might be displayed on an oscilloscope, in this picture.
Just a plain, ordinary tone.
Now place your mouse cursor here. That tone is also at a constant frequency of 700Hz. The difference is that its amplitude (its size, its volume) is being changed, increasing and decreasing alternately. It can be seen graphically in this picture.
In a sound wave this is tremelo. In a radio wave it is amplitude modulation (a.m.) They're the same thing.
And now place your mouse cursor here. This time the note's frequency is not constant. Although centred on 700Hz it is being changed, increasing and decreasing alternately, and can be seen graphically in this picture.
In a sound wave this is vibrato. In a radio wave it is frequency modulation (f.m.) They're the same thing.
Many musicians are confused over temolo and vibrato. It should come as no surprise, therefore, that the people who mess around with our dictionaries are too.
Ok, have you just scurried off and consulted yours? They may have got near the mark with vibrato but I bet they have much more to say about tremelo and I bet it isn't as simple as the correct definition which I have just given.
Your dictionary isn't always right. While some countries fiercely defend their language against misuse and at least one even has a national institute to protect it, we don't, and our dictionary editors are quite happy to follow the illiterate herd and meekly modify meanings in accordance with the latest fads, fashions and grotesque linguistic abberations.
