I had two sessions yesterday and they represented the wide range of this kind of work.
The first was for an American writer. He’d sung a verse and chorus into his phone as he was driving and wanted an acoustic guitar accompaniment for it. Coincidentally, I’d done the same thing a few days ago: on a drive back from Bristol I’d been listening to some reference tracks for a library music brief that had just come in and a song started coming to me. I recorded my voice singing the bits as they appeared and demo’d it the next morning.
The challenge here was to extrapolate the chords, groove, and tempo from his vocal. I listened to it a few times without a guitar in my hand and figured out the harmonies. The tempo was pretty solid, so I put the in-car recording on a track in Pro Tools, used a noise reduction plug-in to get rid of as much of the road/engine noise as possible, and got to work.
I sent him two versions as mp3 files for approval: one strummed and one picking. He chose the picking one but asked for the tempo to be reduced by 10 BPM. I re-did it as requested, this time using two mics, and sent him the full-bandwidth wav files. Bingo: he paid me within 12 hours.
The second session was the latest in a series I’ve done for a Danish producer: in contrast to the in-car recording, this track was fully-produced and sounded good already. I suggested some power chords and effects and he asked for a specific synth line to be doubled.
As with the other session, I sent mp3s of the ideas and he approved them with a couple of minor tweaks. Wav files are on their way to the client as I write.
The principles I applied to these sessions are always the same: do more than is asked for, be non-defensive about requested changes, send mp3s for quick approval, communicate with the client regularly and promptly.