I'v not been playing long, but can play a few tunes- however, the easiest of all, smells like teen spirit- I'm finding impossible!

It's not hitting the notes, as I can *play* the entire track- it's getting the damn rhythm right!
I play the intro (clean) bit with: D U D, then D U D U(MUTED) then D D.
However, when the distortion comes in, the tabs I use (about 4 different ones!) tells me to keep this same picking pattern, but when listening to the track, it sounds like there's only 2 muted picks (D U), followed by a D U D, as opposed to the D D when it was clean.

Sorry if I'v not explained this very well, ideally, if you play it and it sounds right, can you say what your strumming pattern is for the main riff?

It's not "the easiest of all" at all so you can happily dispel that myth.

It's fiddly, it's not a "beginner" song at all - the strumming pattern is awkward, the timing isn't quite what you'd expect and muting with the left hand isn't something you can even attempt until you've already got yourself some way competent with fretting ang changing chords.
Actually called Mark!

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left hand muting!?
I'v got the muting sounding okay using normal palm muting- I'll try doing left hand muting instead next time I play it.
Don't do one or the other. Both kinds of muting are essential to a good sound and should be used when applicable. For example, left handed muting technique is good for muting the upper strings and when changing chords; right handed muting is good for separating notes and chords and keeping the lower strings quiet. Neither one can stand in for the other.
Sometimes when learnin rhthym, its important not to get too stuck on the DU business and play around with it, listen to live versions. Kurt Cobain certainly had fun, rather than sticking to "D U D, then D U D U(MUTED) then D D"
You'll get it, I can play that song infinitely times better than when I first could play it well.
I wouldn't nessecarily listen to live Nirvana if you want to learn the guitar riffs. Kurt purposely threw wrong notes in there to mess with Dave. Stick to the studio first, then add that grungey messed up tone. As for the picking, try doing a few less or extra scratches in there to see if it sounds better. I had to mess around with them from the tabs until I finally got it to sound right in my opinion.
First off tabs aren't always correct, especially when it comes to timing and muting. Use them for the notes and figure the rhythm and tempo by ear.

SLTS is not the easiest song to learn. I remember struggling with it too.

Those muted "dead" notes should come in naturally without thinking about them. If you're conscious of each one and playing them like you play the fretted notes you're missing the point. Don't think "oh I need 3 dead notes there, not 2". Thats not how it works.

It's all in the right hand. Without fretting, just loosely touch all the stings to mute them with your left hand, strum with your right hand. Treat it like a drum.

Watch this video, most of it might be over your head, but it's the concept that matters.

Just pay special attention to the lesson at 1:50.

Hes using all down strokes but the same can be applied with alternate strumming. Try to get your right hand to "dance" to a rhythm. Be conscious of them temp and tap your foot to the beat. Get the idea of rhythm and time in you head and just strum. Get into it.

Once you have the beat in your mind and your right hand is strumming away start using your left hand to add notes to the beat. When you press down with your left hand you hear the notes, when your hand is relaxed they muted. There is no palm muting here. It's all left hand.

Get the idea of the beat in your mind and practice bringing your right hand up to grips with timing and rhythm.

look at this too around 1:45. Again, it'll be over your head and probably not your cup of tea, but the right hand is sooo important when it comes to the beat.

Hope this helps.

Quote by Expandingmind
Sometimes when learnin rhthym, its important not to get too stuck on the DU business and play around with it, listen to live versions. Kurt Cobain certainly had fun, rather than sticking to "D U D, then D U D U(MUTED) then D D"

Oh, this.

Unless you're really anal about the tone you're getting and your upstrokes and downstrokes are vastly dissimilar, there's no need to fret about which chords are down and which are up. Just do what sounds correct. Get the rhythm and technique, THEN worry about the tone.

Edit: I understand that TS is not doing this DUD business for tone, but I'm just saying some do.