[chuck] std.mtof?

hi world. i've been dabbling for a while with chuck now, and have a little doubt i've seen this in various of the provided examples (this one is from the band-o-matic.ck // pentatonic 2 * std.rand2( 0, 4 ) => int freq; if( freq == 6 ) 7 => freq; if( freq == 8 ) 9 => freq; std.mtof( (float)( 21 + std.rand2(0,5) * 12 + freq ) ) => band.freq; if ( std.randf() > 0.7 ) std.rand2(0,3) => band.preset; } and i see that it generates a pentatonic scale (in fact i've used it as provided and works). But i don't really understand how it works. i can get the first three lines, but i don't now what std.mtof is for, so i can't guess what it is for. any kind helping hand? thanx a lot. the deeper i know chuck, the more i love it!! cheers!