I need to play in D on some tunes and dont want to detune my Gibson, so I use my Ric for "D" stuff and switch over. I dont do it very professionally at all, i turn volume to 0, pull the guitar lead out of the amp, put down old bass, pick up new one, plug lead into new bass, plug lead into amp, set EQ / gain etc to match the new bass (ive had to memorise it lol) and then 'orf ya go. professional? probably not