Backmasking

All right. Some people may be familiar with the Led Zeppelin Song "Stairway to Heaven" enough to have heard about backwards satanic messages in the song. Here's a webpage that demonstrates it. The verse that most people point to as having backwards lyrics go as followed:
if there's a bustle in your hedgerow
don't be alarmed now
it's just a spring clean for the may queen
yes there are two paths you can go by
but in the long run
there's still time to change the road you're on

Upon listening to it myself backwards, the lyrics seem fairly clear and go as follows

Here's to my sweet Satan
The one whose little path would make me sad whose power is Satan
He'll give-He'll give you 666
There was a little toolshed where he made us suffer sad Satan.

That's a pretty long string of words (not just a "Satan" here and a "Satan" there that could've been generated randomly) that make sense. And if it were intentional, it would be pretty impressive, especially in the time it was written since technology was not as sophisticated as it is now. I naturally assumed that it was intentional because of its length and because of the way he pronounces his words (covers don't usually get it right and the message doesn't sound as satanic) But I thought to myself: is it really intentional? Why don't I use my knowledge of linguistics to find out? Keep in mind that, if you don't know much about linguistics, you might want to check out how to understand the symbols and how to get IPA fonts here, because from here on, I'm going to assume that you know what the heck I'm talking about.



Preparation
Someone once told me that, when played backwards on any recorder, plants (/plænts/) sounds like snails (/sneɪlz/) backwards and vice versa. I tried this out and it was true (you can check it out on your computer, just go into your friendly windows sound recorde program, record it and then reverse it). Now there are some very important elements in why this is so. Firstly, English does a very good job of making voiced sounds like /z/ /d/ and /b/ into voiceless sounds like /s/ /t/ and /p/. We don't think of them as such because of methods like aspiration and length of sound segments that cue speakers and listeners into which one it is. Secondly, not only are /æ/and /e/ similar, but, in this example, both words would have the vowels nasalized. Although /eɪ/ is technically a diphthong, it's possible that either a) [plɪænts] doesn't sound too different from the way plants is normally said or b) the word snails has a more rapidly articulated I in the diphthong. Some phonologists prefer to omit the i in transcribing English since /e/ rarely is seen by itself in American English utterances. The most important factor, though, is the human tendency to find patterns. 
So I thought to myself, maybe certain sounds sound like something slightly different backwards. Really, though, the only sounds that would sound different would be stops and diphthongs. So I recorded the stops that we have in English and found that, in general, aspirated stops like [pʰ] and [kʰ] sound like fricatives of the same place of articulation-- [ɸ] and [x] respectively. Unaspirated and voiced stops sound like unreleased stops, and could be interpreted as both voiced and voiceless. The glottal stop still sounds like a glottal stop. I also took a look at a palatal nasal, since it always seemed like it was followed by an epinthetical [j]; to my ears, it sounded either like /in/ or /iŋ/
I concentrated on diphthongs of rhotic English, since that seems to be the predominant dialect of the song's vocalist. They go as followed:
/eɪ/ becomes /je/
/oʊ/ becomes /wə/
/ɔɪ/ becomes /jo/
/aʊ/ becomes /wæ/ or /wɑ/

As a side note, I'd like to point out that since Russian orthography has letters that represent the /jo/ /je/ and /ja/ sounds (they also function as palatization markers) that I would imagine these sounds are common in the language. In addition to the language's inclusion of a velar fricative /x/ that to us sounds like they're bringing up some phlem, I would imagine that a lot of backwards music might sound a bit like Russian. Maybe Russian music sounds like English backwards. That puts a whole new perspective on the Cold War.

Data
So, with all that in mind, I first transcribed the entire song forwards using IPA. Then I both listened to the song backwards and applied my rules that I had established above to transcribe it backwards. It was a long vacation, so I had time.
Here is the first verse forwards as an example:

[ðeɹ.zəˈleɪ.di.huz.ʃʊə]

[ɑl.ðaʔ.glɪ.tʰɹ̩.zɪz.gold]

[æ̃n.ʃiz.bɑː.jĩ.ŋə.steə.weɪ.tʰə.hɛ.və̃]

[wɛ̃n.ʃi.gɛts.ðɛɹ.ʃi.nowz]

[ɪf.ðə.stoɹz.ɑː.ɹɔʟ.kl̥owz]

[wɪ.ðə.wəːd.tʃi.kʰɛ̃n.gɛʔ]

[wʌʔ.ʃˑi.kʰeɪ̃m.foː]

[uː.ə̃n.ʃiz.bɑː.jĩŋ.ə.steə.weɪ.hɛvə̃]

Note that there are some elements of rhotic and non-rhotic dialect intermingled (see first verse)
Now here it is backwards (the order is backwards too so if you want to compare you've got to go bottom up):

[ə̃vɛ.hjew.əets.ə.ŋĩj.ɑːb.ziʃ.nə̃.uː]
[oːf.mjẽx.iˑʃ.ʔʌw]
[zwən.iʃ.dəːw.əð.ɪw] 
[zwəl̥k.ʟɔɹɑː.zɹots.əð.fɪ]
[zwən.iʃ.ɹɛð.stɛg.iʃ.nɛ̃w]
[ə̃v.ɛh.əs.jew.əets.əŋ.ĩj.ɑːb.ziʃ.næ̃]
[dlog.ziz.ɹ̩s.ɪlgʔað.lɑ]
[owʃ.zuh.id.jel.əz.ɹeð]


Fairly regular. Keep in mind that I've made the transcription fairly narrow, mostly because I don't know what's obvious with backwards phonetics. Now here's the juicy verse
Forwards:

[ðeɹ.zəˈleɪ.di.huz.ʃʊə]
[ɑl.ðaʔ.glɪ.tʰɹ̩.zɪz.gold]
[æ̃n.ʃiz.bɑː.jĩ.ŋə.steə.weɪ.tʰə.hɛ.və̃]
[wɛ̃n.ʃi.gɛts.ðɛɹ.ʃi.nowz]
[ɪf.ðə.stoɹz.ɑː.ɹɔʟ.kl̥owz]
[wɪ.ðə.wəːd.tʃi.kʰɛ̃n.gɛʔ]
[wʌʔ.ʃˑi.kʰeɪ̃m.foː]
[uː.ə̃n.ʃiz.bɑː.jĩŋ.ə.steə.weɪ.hɛvə̃]

[ə̃vɛ.hjew.əets.ə.ŋĩj.ɑːb.ziʃ.nə̃.uː]
[oːf.mjẽx.iˑʃ.ʔʌw]
[zwən.iʃ.dəːw.əð.ɪw]
[zwəl̥k.ʟɔɹɑː.zɹots.əð.fɪ]
[zwən.iʃ.ɹɛð.stɛg.iʃ.nɛ̃w]
[ə̃v.ɛh.əs.jew.əets.əŋ.ĩj.ɑːb.ziʃ.næ̃]
[dlog.ziz.ɹ̩s.ɪlgʔað.lɑ]
[owʃ.zuh.id.jel.əz.ɹeð]

[ɪf.ðeə.zə.bʌ.sl̩.ɪ̃.ɲjə.hɛdʒ.how]
[dow̃ʔ.bi.ə.lɑ̃ːŋ.næ]
[ɪts.dʒʌst.ei.spɹ̥ɪ̃ŋ.kl̥ĩn.foɻ.ðə.meɪ.kw̥i]
[jɛs.ðe.ɹaː.tʰu.pæz.ju.kɛ̃n.gow.ba]
[bʌɾ.ɪ̃n.ðə.lɔ̃.ŋɹə̃n]
[ðeəz.stɪl.tãm.tə.tʃeɪ̃ndʒ.ðə.ɹowʔ.jɹ̩.ɔ̃n]

Backwards:

[nɔ̃.ɹ̩j.ʔwəɹ.əð.ʒnjẽʃ.ət.mãt.lɪts.zəeð]
[nə̃ɹŋ.ɔ̃l.əð.nɪ̃.ɾʌb]
[ab.wəg.ŋɛ̃k.uj.zæp.us.aːɹ.eð.sɛj]
[iwk.jem.əð.ɻof.nĩl̥k.ŋɪ̃ɹ̥ps.je.tsʌʒ.stɪ]
[æn.ŋɑ̃ːl.ə.ib.ʔw̃əd]
[wəh.ʒɛ.həjn.ɪ̃.l̩s.ʌb.əz.əeð.fɪ]

Conclusion: 
Well, I guess it wasn't done on purpose. I mean the guy couldn't have done it the way I thought he did it. I would expect the backwards message to be more like this:

[ieʒtəmaswiʔseʔn̩]
[ðowɔ̃nuzlɪɾowʔ]
[ab.wəd.meɪx.jʊ.zæv.uz.pawɹ̩ɪzeɪʔ]
[jugɪvzɹ̩ʔŋixniɹsɪksəʒsɪk]
[ænwɔzl̩ɪʔwəz]
[wəʃeɪ.ə.ineɪdʌsəfə.sæd.seɪʔ]

Now that would be convincing and that's how it sounds at first. Especially when you see the similar features of the segments in what it sounds like and how the words they seem to represent are actually pronounced in real forwards speech. So it's really the devil within us.
For enjoyment's sake. Here's the whole song in IPA:


[ðeɹ.zəˈleɪ.di.huz.ʃʊə]
[ɑl.ðaʔ.glɪ.tʰɹ̩.zɪz.gold]
[æ̃n.ʃiz.bɑː.jĩ.ŋə.steə.weɪ.tʰə.hɛ.və̃]
[wɛ̃n.ʃi.gɛts.ðɛɹ.ʃi.nowz]
[ɪf.ðə.stoɹz.ɑː.ɹɔʟ.kl̥owz]
[wɪ.ðə.wəːd.tʃi.kʰɛ̃n.gɛʔ]
[wʌʔ.ʃˑi.kʰeɪ̃m.foː]
[uː.ə̃n.ʃiz.bɑː.jĩŋ.ə.steə.weɪ.hɛvə̃]
[ðeə.zə.saɪ̃n.ʔɑ̃n.ðə.wɔʟ]
[bʌ.tʃi.wʌ̃nts.tʰə.bi.ʃʊə]
[kʰʌ.ʒju.now.sʌ̃m.tʰãmz.wəːdz.hæv.tʰu.mĩnĩŋ]
[ɪ̃.nə.tʃɹi.baɪ.ðə.bɹʊk]
[ðɛ.zə.sɔ̃ŋ.bɹ̩d.hu.sĩŋz]
[sʌ̃m.tʰaɪ̃mz.ɔː.ləv.ɑː.θɔts.ɑː.mɪs.givə̃]
[uː.ɪʔ.meɪks.mi.wʌ̃n.dəː]
[uː.ɪʔ.meɪks.mɪ.wʌ̃n.dəː]
[ðeə.zə.fi.lɪ̃.na.gɛʔ]
[wɪ̃.na.lukʰ.tʰʊ.ðə.wɛst]
[æ̃n.maɪ.spi.ɹɪʔ.iz.kɹa.jĩŋ.foɹ.li.vĩŋ]
[ɪ̃n.maɪ.θɔts.aɪ.hæv.sĩn]
[ɹĩŋ.zəv.smowkʰ.θɹu.ðə.tʃɹiz]
[æ̃n.ðə.vɔi.sə.zəv.ðowz.hu.stæ̃n.lʊ.kʰĩŋ]
[uː.ɪʔ.meɪks.mi.wʌ̃n.dɹ̩]
[uː.ɪʔ.ɹɪ.li.meɪks.mi.wʌ̃n.dəː]
[æ̃n.dɪts.wɪ.spɹ̩.ðaʔ.tsũn]
[ɪf.wi.ɔʟ.kʰɔl.ðə.tʰjũn]
[ðɛ̃n.ðə.paɪ.pɹ̩.wɪ.liɾ.əs.tʰʊ.ɹi.zə̃]
[æ̃n.də.nju.deɪ.wɪl.dɔ̃n]
[fə.ðowz.hu.stæ̃n.lɔ̃ŋ]
[æ̃n.də.fɔɹɪsts.wɪl.ɛ.kʰə.wɪð.læf.tɹ̩]
[ɪf.ðeə.zə.bʌ.sl̩.ɪ̃.ɲjə.hɛdʒ.how]
[dow̃ʔ.bi.ə.lɑ̃ːŋ.næ]
[ɪts.dʒʌst.ei.spɹ̥ɪ̃ŋ.kl̥ĩn.foɻ.ðə.meɪ.kw̥i]
[jɛs.ðe.ɹaː.tʰu.pæz.ju.kɛ̃n.gow.ba]
[bʌɾ.ɪ̃n.ðə.lɔ̃.ŋɹə̃n]
[ðeəz.stɪl.tãm.tə.tʃeɪ̃ndʒ.ðə.ɹowʔ.jɹ̩.ɔ̃n]
[ɑ̃n.ɪʔ.meɪks.mi.wʌ̃n.dɹ̩]
[jɔ.hɛ.dɪz.hʌ̃.mĩn.ʔæ̃n.ɪʔ.wow̃ʔŋ.gow]
[ɪ̃ŋ.kʰeɪ.ʃju.dow̃.now]
[ðə.paɪpɹ̩z.kʰɑ.lɪ̃n.ju.ɾə.dʒɔɪ̃n.hɪ̃m]
[diɹ.leɪ.di.kʰæ̃.ɲu.hiɹ.ðə.wɪ̃n.blow]
[æ̃n.dɪ.dʒju.now]
[jɔ.steɹ.weɪ.laz.ɔ̃n.ðə.wɪ.spɹ̩.ĩŋ.wɪ̃ːə̃ː]
[æ̃n.dæ.zwi.waɪ̃n.dɔ̃n.daw̃n.ðə.ɹowd]
[ɑː.ʃæ.dowz.tʰɔ.lə.ðɛ̃.nɑː.sowl]
[ðeɹ.wɑʟk.sə.leɪ.di.wi.ɑl.nəːw]
[hu.ʃaɪ̃n.zwaɪʔ.laɪɾ.æ̃n.wʌ̃nts.əv.ʃow]
[haw.ɛv.ɹi.θĩŋ.stɪl.tɹ̩̃nz.tʰə.gow]
[æ̃n.dɪ.fju.lɪs.ə̃n.vɛ.ɹi.hɑːɹ]
[ðə.tʃɹu.wɪʟ.kʌ̃m.tə.ju.æʔ.lɑs]
[wɛ̃.nɑ̃l.əɹ.wʌ̃n.æ̃n.wʌ̃.nɪ.zɑː.ʎæ]
[tʰʊ.bi.ʔə.ɹɔkʰ.æ̃.nɔ.tʰə.ɹəːʊː]
[ə̃n.ʃiːz.bɑː.jĩ.ŋə.steə.weɪ.tʰu.hɛ.və̃]