Some related topics:
-Cymatics (Study of Vibrations on Different Mediums):
http://www.youtube.com/watch?v=alT1KfE8_sk
-The Hidden Message in Water (Water Molecules React to words/symbols attached to container - Mentioned in Movie: "What the Bleep do we Know"):
https://www.youtube.com/watch?v=tAvzsjcBtx8
I'd think that it wouldn't hurt to try. I wonder what fundamental frequency would stimulate the plants the most. There are some musicians who believe that Concert A (being = 440hz in America) should be tweaked, and that humans respond more sensitively to music played on instruments tuned to A=432. Perhaps this is good for cannabis as well, as some promoters of A=432 claim that the sun and moon express itself in ratios of 432.
Also, an earlier comment about it affecting the water might have justification in the above research by Dr. Emote.
Mine like reggae and good hip hop. Not radio crap. classical too. That article does not make sense about tempo. Classical and rock are both faster than rap. Rap is always in 4/4 , classical, 6/8, 11/16, rock is what ever and usually never steady. Most bands don't know how to play to a click. Then jazz is all over the place.
Im an audio engineer ( mixing , mastering, recording , and post production)
I think that they're referring to the Tempo, as in 1/4note=120 (or 120 bpm), or 1/4note=90 (90bpm) etc. You're referring to time signature (4/4 time, 6/8 time) which is purely a function of what note gets the beat and how many beats in a phrase (i.e., in 4/4 time, one 4 refers to which note equals a beat and the other 4 refers to how many of those notes equals a bar). You can have a piece written in 3/4 time (or 12/8 ) but with a tempo of 120bpm. You can also have another piece in 3/4 time with a tempo of 90 bpm; the latter being considered "slower" than the former.
Think about Bach's second movement to his Orchestral Suite no. 3 in D Major, BWV 1068 (Also know as Air on the G String). It is in Common, or 4/4 time, and it's tempo is "Lento" or Slowly, which is about 40-45 beats per minute.
http://en.wikipedia.org/wiki/File:Air.ogg
Compare this to Outkast's "Hey-ya" which is also in 4/4 time but the tempo is probably
"Prestissimo" (Very Fast) at around 180 beats per minute.