Hi all, I'm relatively new here and wondered if anyone could advise me

Basically, we've drafted in a bass player for a couple of gigs as a temporary measure but he doesn't really fit the style of music - but he's the only one available. Whereas our songs are very 60s like (so simple bass lines that serve only to compliment the whole song - some repetitive, some single notes held for 4 beats etc), this player tries to do super fast hammer ons when it only needs the 5th to 3rd fret on one string, for example.

How can I explain (without offending) that it's too much without making him lose interest? He doesn't seem to be getting the message that the rest of us are playing simple parts - probably due to the "if I play fast it must be good" mentality...

Anyway, thanks in advance for any input
Well... You drafted Him... Just be honest, and respectful... finish a song in rehearsal, then start... "Ok, that was pretty good, but"... then tell him how you'd like him to play the song, and then play it again... if he doesn't change anything, stop in the middle and correct.. don't chastise... There's always the possibility that he's gonna do it his way anyway, but at least if you have to send him on his way, you at least gave him a shot at doing it your way...
I Play Guitar
Some Like it
Some don't
I don't care
Beats Workin'
Pretty much as been said, stay respectful, don't criticise him, don't be in any way a douche.
This seriously severs relationships (from experience of people acting this way to me).

Tell the dude that he needs to bring it back a bit.
Maybe allow one song in the set for him to go nuts.

When I played bass for a band (funnily enough one of the ones that had a dude who acted a douche ) the whole set was suuper boring, more boring than what this guy would think your set is. I did try to spice up some of the bits (while making it still fit of course). But there were two songs which were a bit more ambiguous on the bass, so I got to do all the jazzy stuff I love to do on bass on those two songs and those tracks managed to peak me enough to allow the boring stuff...if this makes sense!

Hope I've helped.
Tell him his playing is too busy. Are you guys going to have a practice before anymore gigs to kind of get him to understand what you want him to do? If so try to find some middle ground. Explain to him that he can't get all crazy with your songs. But do say "ok during these parts you can cut lose some and have a solo".

Don't consider him as a future substitute. Thank him and if he asks tell him he doesn't fit with the style. That's all.

If he can't handle playing simple bass lines and playing them with the right feel his more active playing is probably off and sounds bad anyways.
You just sit down and talk to the guy.

"We like you're playing and you're good at it, and a lot of that stuff is interesting, but it's not really consistent with what we're trying to do as a band. Do you think you could play something simpler? We're trying to do more of a '50s rock'n'roll thing."

Either he gets it and goes along with it, or you decide he's not the bassist for you.

That being said, sometimes it's important to give somebody a time in the set when they can do their thing. If you give him a song when he can show off, he may be less inclined to try to work that into all his other songs.
How do his parts sound?

You're in a band, broseph. Making music is a creative process! Maybe he is on to what will be the next huge resurgence of classic rock tuneage!

Playing fast doesn't make you good... but it doesn't necessarily make you bad either. Work with him and develop your own kick ass style.

So my overall advice is:
Don't tell him anything. Work with him to make sometime special. Everyone has their own musical influences... the blending of those influences is what makes bands original and interesting.

Music is a wonderful thing, inn'it?
Without helping your problem at all, 60s rock bass parts can be awesome. Listen to the who, maybe you could steer him like that so that he can get his fun basslines and you get your 60s rockingness.