Guitar Amplifier - Use With Other Instruments

Use With Other Instruments

Musicians often run sound-sources other than guitars through guitar amps. For live performances, synthesizers and drum machines or keyboards are often put through guitar amps to create a richer sound than can be obtained by patching the direct-outs right into the PA system. Guitar amplifiers can add tonal coloration, roll off unwanted high frequencies, and add overdrive or distortion. Deep Purple's Jon Lord played his Hammond Organ through a distorted Marshall amp to create a sound more suitable for heavy rock. String instruments and vocals are also put through guitar amps to add distortion effects. Some blues harp players also use guitar or bass amps to create a warmer overdrive sound for their harmonica playing; 1950s-style "tweed" amps are often used for this purpose, such as Fender Bassman combo amps.

Recording engineers occasionally run pre-recorded parts through miked guitar amps, a process called re-amping. When a guitar part is recorded "dry" (e.g., without effects or distortion), straight into the mixing board for a recording, this gives the producer and mixing engineer much more flexibility to create new re-mixes or new tones from the recording. If a guitar player records an electric guitar part that is run through a chorus pedal and a distortion pedal, there is little that can be done at the "mix-down" stage to change the sound of this recording, beyond "tweaking" the equalization and modifying the level. Since re-mixing or mixdown can take place weeks, months, or even years after the original recording session, it may be impossible to have the guitarist come in to re-record a new part.

If the dry guitar sound is recorded, though, the mixing engineers can add any effects they want to the signal and then re-play it through a miked guitar amplifier which is being recorded. The effects, amplifiers, cabinets, and miking processes can be changed to any combination. When a dry guitar has been recorded, it can be a useful tool for "updating" an older recording. For example, if a band wants to re-release a 1980s-era album on which the guitar has a very dated 1980s sound, with heavy flanging and artificial-sounding electronic distortion, the band can update the guitar sound by re-amping the dry signal and using 2000s-era effects.

Mixing guitar amp signals with other signals is also done by some musicians. Chris Squire of Yes produced his bass guitar sound by playing through a guitar amplifier with its bass turned down, treble turned up, and volume turned up well into distortion; the miked guitar speaker signal was then mixed with a direct-input (DI) signal, a technique that has been used for processing synth keyboards as well. A bass guitar can also be played through a bass amp in parallel with a distorted guitar amp by using a DI box; the bass amp provides the low frequencies, while the guitar amp – which is not capable of reproducing the lowest frequencies of the bass guitar– emphasizes the upper harmonics of the instrument's tone.