Alright, this topic will probably only appeal to fellow musicians, but it's one that has been bothering me for a long time.
I first started playing guitar because I was listening to guys like Eric Clapton, Duane Allman, Pete Townshend, Jimi Hendrix, Jimmy Page, etc. Their music appealed to me a hell of a lot more than whatever it was that I was listening to before that (mediocre indie bands), and I loved listening to live recordings of these guys- they put out some of the best live albums ever (Clapton in Cream with Wheels of Fire and Live Cream, Duane Allman in the Allman Brothers with At Fillmore East, Pete Townshend in the Who with Live at Leeds, etc).
If there's one thing that all of those players have in common it is that they improvise every solo they play (for the unaware, "improvise" just means that they make it up on the spot). So naturally, when I began playing the guitar, I just always knew that you were "supposed" to improvise your solos. It never occurred to me that you might play the same thing every time, honestly. Obviously I learned some solos note for note, but I just assumed that when I got in a band I would improvise because that's what all my heroes did.
The first full song I learned, like a lot of people, was "Stairway to Heaven." The guitar solo in that song is legendary. It's a magical melodic masterpiece. Everyone knows it. It's probably the most renowned solo on any instrument ever.
But when playing it live, Jimmy Page always improvised it.
Yeah, the first couple measures are about the same, and the ending is the same, and there's that repeating lick in there that he always plays, but everything else is wide open.
Like most budding rock guitarists, I spent hours learning the studio version of that solo. But I spent many more hours improvising in the key of A minor over the song. Like anything in music, improvisation is a skill that needs to be honed and I've spent countless hours attempting to hone it (with mixed results).
Fast forward a few years and I "discover" Guns N' Roses. Also around this time I am listening to a lot of Rush and I greatly admire both Slash and Alex Lifeson. I look up live videos of these two great musicians and I discover that every solo they play live is almost identical to the one they played on the record. And I'm baffled.
Perhaps the MOST baffling part is that these two guitarists, Slash and Alex Lifeson, had the same influences as me. They were all into Clapton, Hendrix, Page, Townshend, et al. Now to this day I still do not understand why they do not improvise like their heroes did. It can't be that they think people expect to hear the same solo as they recorded on their album and will be disappointed if they don't...because Jimmy Page clearly never had that problem. So what is it?
Now, we all know that music is an expression of emotion. Maybe more accurately, a communication. To me it seemed obvious that when you play a guitar solo it should very much be in the moment- you should be expressing or communicating what you feel as you're feeling it, and not trying to replicate what you felt a year or a decade ago when you recorded the song.
Of course, you can express yourself by playing composed music...that's what all the classical players do. But to be honest, I am not interested in classical music for that very reason. It's not coming from the player, it's coming from some dead white guy from hundreds of years ago. But that's a different story.
Now, there are certain cases where I can see that playing a guitar solo note-for-note can be great. There are some solos that are just so good you know you'll never top them so you might as well not even try (but again, that never stopped Jimmy Page). There are some solos that are more than just solos...they're melodies, they're themes for the song. Take "Estranged" by Guns N' Roses. Slash composed melodies on the guitar that are integral to the song. You wouldn't want to improvise those. I also saw an interview with Tony Iommi, the guitarist from Black Sabbath, who made that same comment about one of his solos in "War Pigs." It sounds more like a riff than a solo, really, and it sort of just became another riff of the song, so he played it the same way each time.
These cases are excusable. But everything else? Well, in my opinion they should be improvised. But that's not going to stop me from seeing these artists who don't improvise live. I've already seen Slash once and am going to again next month, and I'm going to be seeing Rush in April. I'm sure the shows will be great, but think of how much greater they might be...