You mention "dry, snappy" as adjectives. One of the things that degrades with strings is the richness of partials and also the amount of sustain and power. I wouldn't take your isolated results to be significant other than you happened to like the older strings. Perhaps those type of strings were simply better suited to the dynamics of that particular instrument. As you know the amount of variation for strings is pretty large. My wife just changed the strings on her electric bass to round wound versus flat wound to achieve better results playing for NYE concert. She is not an electric aficionado but it was definitely different and better for that gig.

Usually,you want fresh strings (that have been played a few hours, ..off stage) to get all of what the player and the guitar have to offer. In the mix, it can well be that some of those qualities will be filtered out and modified. But at least you have the choice and you can reach and change the sound to what you want with ease. This is not always easy with old strings.

Also: if a string brakes ..do you have a similar old string in spare? The sound playing with mixed old and new strings is a pain. So, do you then put on new ones? Can you still continue reording, if you need the same sound on all parts or on all songs?

Both perpectives are well taken. And it may well be instrument specific. Out of habit, I always keep a few old sets in the cupboard for just such occasions so replacing one string with an equivalently aged one does not pose much of a problem.

But the phenomenon can be interpreted in more than one way. You say: One of the things that degrades with strings is the richness of partials and also the amount of sustain and power which could be restated as one of the things that improves with strings (aging) is the clarity of the fundamental and also the rate of decay. To be sure, certain instrument voices depend a great deal on rapid decay, like drums, and even violin (it is known that many better violins dissipate energy faster than cheap violins, and this advantage is due to excitation from the continuous energy input of bowing, which is fundamentally different than the momentary energy input from string picking) and so it may be with some accoustic guitar models.

My only point was that it may not be a universal law that new strings will always sound better than old ones on a guitar, when being recorded as opposed to live performance, and that it would appear to be guitar and material dependent. There may well be styles of music and circumstances where well aged strings would sound better on tape, and this is new information to me.

Somewhere in the Guitar Player archives there is an interview with Robbie Krieger from the Doors who indicated that he never changed his strings.

Dont know if this was ancient smoke blowing or what....

Back in the day when I was getting to be talent instead of engineer, I would keep all of my bass strings, label them with date changed, bass they were on, and some pertinent info about how they sounded when I changed them out. On a couple of occasions, I used this info and changed out a newer set for an old crusty used set to record with. Most of what I was needing was the length of decay.

Part of the problems associated with old strings is the LOSS of the fundamental after a length of time. Bass strings are especially subject to this. A regular wipe-down after play helps for adding time to the aging process but will never prevent the eventual demise.

I'm with K on the choice factor. With the old strings it is what get is what you get. It may or may not work. I think that for acoustic instruments this isnt as much of a problem as with electric. Getting the amp to act like you want it to, both with output and tonal structure , depends solely on how much signal you can get into the front end.

I agree it is instrument and material dependent, but I would rather have an instrument capable of different modes than one stuck in a singularity without a chance of change of tone or attack. That said, certain types of magic happen no matter what the parameters applied.