What does it mean to "KNOW" how to play a song to you?

Wow it could be different for each song but for me it's usually picking one of the guitars and go with that. You most likely have a rhythm and lead guitar if more than one along with multiple layers or guitars on recodrings. I don't usually mess with those unless one is playing a very recognizable lick that needs to be played then I might replace that were say the rhythm guitar might just be playing some chords.

I started and still am a predominantly rhythm player not so much by choice but just cuz that's my skill level but I am slowly learning more solos.

But the rhythm guitar is the place to start as there sometimes are alot of dead spots for the lead guitar so you have to play something.

In a simple single guitar arrangement I would learn the rythym for the whole song and then instead of playing the rhythm for the solo you play the lead then back to the solo.

For me, it's lots of things.

It's being able to pick up my guitar and play the piece from beginning to end, without forgetting how the next bit goes or getting lost, reasonably close to tempo, accentuating the melody rather than all the notes being played at any point in time sounding muddy, and it being recognisable to somebody else.

It's feeling sufficiently happy with a recording to put it out there for public scrutiny

And there are non-me factors too:

It's somebody singing/ humming along as I play

It's somebody who you don't know coming up to you and saying "Thanks, that was nice."

It's somebody clapping when nobody else bothers.

I'm a solo classical guitarist, so my music comes oven ready; someone else has done the single guitar arrangement. I do tweak certain bits where I think the arrangement is weak, but not very often.

A :-)

there's different levels of knowing a song. you can know it note for note off the recording or sheet music. you can know the skeleton, the chords and melody and lyrics. or you can have played it enough that it's developed its own style and personality, distinct from the original.

Well I just learned my first song.... kinda..

I can play a basic vertion of it all the way through... I know all the words... I can play the song, and sing it at the same time. Do I do a good job??? Well... I need a LOT of polishing time on it yet.... Is it note for note??? No way.... not eaven close.... If you knew the song...would you be able to tell thats what Im playing? Ya, I think so... that works for me. :D In my world to me I know the song.

You know a song when you can play and sing it well enough that no listener cringes and even non-relatives compliment you when they aren't forced to. (My YouTube has pleasantly surprised me that I'm up to this standard.)

The question makes some assumptions about the type of music to be played.
Multiple guitars in the song may or may not be true for things I like to learn.
In fact, a couple of things I do well were recorded as piano accompaniment to a song but come across nicely on guitar. (Dan Fogelberg, Don McLean)

But you can still improve on a song for many years - decades even. Well, at least I can. (Just this week I figured out the signature riff for one of my favorite songs I've been playing off and on for 30 years without the riff. I haven't had the finger skills to do it up until now.)

But what does it mean for you specifically to be able to play a song? And how does one go about making those arrangements for a single guitar?

Most songs do have many layers and use session musicians. Often the songs can't even be reproduced by the original artists themselves in a live performance.

For me, I must say right off that I play along with recordings, almost exclusively iTunes on my computer through its speakers. I use the EQ to accentuate or de-emphasize the vocal, or bass or whatever. So in that case I have those parts in my "performance". I play almost exclusively rhythm, so it's good to have the recording playing leads and solos and bass (unless I'm playing bass along with the recording). Other than that, you make an arrangement that's pleasing to you to play and to hear. In short, make it your own.

I worked on taking Leon Russell's Magic Mirror, written and played on piano, and working it for guitar. There are riffs and fills I cannot possibly play because he is playing them with one hand while playing the chords with the other. Now, I found a Youtube cover that works very well just like I can play it. So, someone else had the same idea I had. And he doesn't play with a recording, he does it solo (rhythm only and a drum machine) and vocal.

Often the songs can't even be reproduced by the original artists themselves in a live performance.

I think this is important. For most of us, it's impossible to recreate the recorded song as a solo player in our own practise sessions so we work on a version which works for us as something we can show to others.

And, if I go to a concert and the stage performance is an exact replica of the CD then I've gained nothing; I might as well have sat at home and played the recorded version.

Interpretation is the word here. You have to know a song to come up with a presentable version but it doesn't have to be the same as the recorded version. If you slavishly attempt to copy every fill, every lick, every note off the recording, then you need to get out more.

i think i may have just found my new sig :D
If you slavishly attempt to copy every fill, every lick, every note off the recording, then you need to get out more.
This is so true though. I used to be so diligent about making sure i had the tab exactly memorised, that to be honest, playing a song did become more about memorisation than any sort of guitar playing skill.

Now i enjoy my playing a heck of a lot more because i deliberately use my own fills, and make my own solo's - unless it is a really well known signature solo that needs to be copied.
I have found to be honest, that nobody notices however differently i play the guitar parts to a song now - so i may as well play them the way i want to :D

There are a lot of levels to this for me.

I know a lot of songs well enough to play at home- with rock, I often play along with recordings.

Many of the songs I play that way, though, I don't completely "know." I know the key, the chords, and enough to get through.

Others, I play "my version." (Solo guitar, me approximating vocals.) On these, knowing the chords, the structure, the words, and how it goes "my way" is enough. THough I might know the original less well than some others, these are the songs I won't hesitate to play at a party when the guitar gets passed around.

Others I play in the band. These, I know my part of completely- could play it in my sleep. But, if it's a song I play bass on, I may know very little of the guitar part, and vice versa. If I don't sing, I don't need to know all the words. And so on.

So I guess what "knowing" a song means depends on what I want to do with it.

Best,
Ande