There are several generalities used to describe electric guitar sustain:
- How long the note rings
- How long you can hear the tone
- It has sustain for days - dude...
Next, you can buy brass nut pieces, brass saddles, steel tremelo blocks, titanium tremelo blocks and depleted uranium pieces but it will only psychologically make your guitar sustain better. The string simply needs a firm anchor point to sit, all else is simple string wave propagation physics.
In this matter; The speed of propagation of a wave in a string (v) is proportional to the square root of the tension of the string (T) and inversely proportional to the square root of the linear density (μ) of the string. This means:
- The string will not decelerate slower because you have a high density tremelo block.
- Will not decelerate slower because your guitar is made of iron, etc...
- The ability to maintain the string tension WILL MATTER.
- String density DOES matter.
- Neck Scale DOES matter.
In Melde's experiment he did not find that changing the density of the weight would increase or decrease wave propagation, i.e., sustain.
One must remember that with electric guitars pickups, the guitar pickup react to the ferromagnetic string excitation of the pickup magnetic field and not the wood body reverberation of the string noise(Caveat: providing there is no piezoelectric pickup on this system). Magnetic pickups are not excited by wood reverberation. Therefore, playing the instrument and feeling and hearing it louder due to replacement blocks and heavy mounting brackets does not equate to longer sustain.
However, one might argue that if you anchored the string ends with balsa wood or Styrofoam (low density material) that sustain will be lost. That is true. But that material is not practical for attaching a string.
A prime example would be the Floyd Rose system. There are certainly two fixed points. The tremolo block is usually made of steel (~8000 kg/m3) verse Titanium (~4800 kg/m3) which will lighten the amount of force require to activate the fulcrum but not increase sustain. Sustain is decoupled from the fixture material.
In conclusion, installing a heavy trem block, brass tail piece, aluminum tail piece, carbon fiber tail piece and guides might make your guitar look good but in will not necessarily improve the sound that flows from your amplifier.