Multilayer ceramincs are great for applications where voltage is constant (ie. your smoothing off a voltage). However they are not good for use inline for AC voltages (i.e. audio and AC signal filters). The reason is that ceramic capacitors will give a piezo electric effect to an AC signal, which causes noise. For audio use a Poly of some type (Polypropelene is best for audio signal pass through).
X7R, X5R
Better than Z5U and Y5V. Typically maintain a capacitance range within +-20% of nominal over the full operating voltage and temperature ranges. As a result they are typically larger and more expensive than Z5U and Y5U types.
Z5U, Y5V
Capacitance drops off severely with applied voltage. A typical Z5U or Y5V capacitor can loose 60% of its rated capacitance with half the rated voltage applied to it.
Z5U and Y5V also exhibit a severe temperature effect loosing more than 50% of nominal capacitance and the top and bottom ends of the temperature range.
