_r_t is a powerful soundfile mixing program  written  by  Paul
Lansky  at  Princeton.  Type    "_r_t"    in a shell window to
launch the program. If you don't want to  lose  the  use  of
this  shell  window while _r_t is running, add an ampersand at
the end of your command line:
                            _r_t &
Extensive _H_e_l_p documentation on how to use _r_t  is  available
within  the program, and we have included a printout of this
documentation within the _S_G_I _M_A_N _P_a_g_e_s binder  in  the  stu-
dios.  In addition, the _F_1 function key, if tapped while the
cursor is positioned over some (but not all) of the  buttons
(such  as  _L_o_a_d _s_o_u_n_d_f_i_l_e or _R_e_l_o_a_d _p_l_a_y_n_o_t_e_s) or in some of
the windows (such as the  _u_s_e_f_u_l  _i_n_f_o_r_m_a_t_i_o_n  and  _P_l_a_y_n_o_t_e
windows)  will  display a terse synopsis, similar to balloon
help on Macintosh systems.

     _r_t includes many of the same  resources  for  soundfile
mixing  as  Oyvind  Hammer's _m_i_x program. Both of these pro-
grams enable one to "preview," in  real-time,  a  mix,  edit
(make  adjustments  to)  this  mix,  then write the mix to a
stereo output soundfile (mono output  is  not  available  in
either  program),  and  save  all of the data used to create
this mix to an _a_s_c_i_i file.

Some major differences between _r_t and _m_i_x include:
     o+ _m_i_x is more graphically oriented than _r_t; _r_t requires
     more typing
     o+ the 2 programs differ  in  signal  processing  (sound
     modification) resources
          => _m_i_x provides post-processing effects such as  a
          delay  line,  filters  and  ring  modulation,  not
          available with _r_t
          => _r_t, by contrast, provides more extensive  tools
          for  processing  individual input soundfiles, such
          as
               pitch shifting, either by a fixed  transposi-
               tion  (_t_r_a_n_s_p)  or  else  by  specifying time
               varying pitch envelopes (_g_l_i_s_s),  and
               reading in only a portion of an input  sound-
               file  (the  _p_l_a_y_n_o_t_e  options _s_k_i_p and _d_u_r or
               _e_n_d)
     o+ _r_t can mix up to 12 soundfiles in real-time; with our
     current  version of _m_i_x  the SGI DACs will sputter with
     this much I/O data

     Generally the first thing one does in preparing  a  new
mix  is  to  specify  all  (or  at least a few) of the input
soundfiles to be used.  From another window, outside of  _r_t,
drag  an icon for the desired soundfile into _r_t's input file
_d_r_o_p _b_o_x, which is located under the _L_o_a_d _s_o_u_n_d_f_i_l_e  button.
(Alternatively,  one  can type in the full path name of this
soundfile in the pink space to the right of this drop  box.)
In the _S_o_u_n_d_f_i_l_e_s window, assign an _s_n_d number to this input
soundfile by clicking on the word  _n_u_l_l  after  desired  _s_n_d
number.   Then  click on the _L_o_a_d _s_o_u_n_d_f_i_l_e button.  Load in
all of the input  soundfiles  you  will  be  using  in  this
manner.

     Most of your subsequent work is done in  the   _p_l_a_y_n_o_t_e
window,  where  one  sets  the  track  number for each input
soundfile, its starting (_a_t) time, an amplitude _g_a_i_n, a  _p_a_n
position  (for mono input soundfiles), and any other desired
processing options.  Tapping the _F_1 button with  the  cursor
in  the  _p_l_a_y_n_o_t_e  window  displays  all  of  the processing
options available within a "playnote" command.  The playnote
line
  _p_l_a_y_n_o_t_e(_t_r_a_c_k=_1, _s_n_d=_1, _a_t = _2._3, _g_a_i_n = ._5, _p_a_n = ._8)
assigns _s_n_d number _1 to _t_r_a_c_k _1. This soundfile  will  begin
playing at time 2.3 seconds into the mix; its amplitude will
be reduced by half (_g_a_i_n=._5); 80 % of  the  signal  will  be
sent  to  the  left  channel  and  20 % to the right channel
(_p_a_n=._8).

     Before you can hear the mix, you must click on the _L_o_a_d
_e_v_e_r_y_t_h_i_n_g  button prepare the mix specifications for execu-
tion. If no errors are displayed within the _u_s_e_f_u_l  _i_n_f_o_r_m_a_-
_t_i_o_n  window, click on the _P_l_a_y button to preview (hear) the
mix. Probably you will not  be  competely  happy  with  this
first attempt. If not, edit the playnote commands, click the
_R_e_l_o_a_d _p_l_a_y_n_o_t_e_s button to update the compiler with this new
data, and play this revised version.

     When you are ready to write your mix  to  a  soundfile,
select  _W_r_i_t_e  _A_I_F_F  _s_o_u_n_d_f_i_l_e under the _S_o_u_n_d_f_i_l_e_s menu, or
else type the _A_l_t key and _g (_A_l_t-_g). Be  sure  to  save  the
output  soundfile  to  your  _s_n_d disk directory, not to your
current working Unix directory on the small system disk.

     All of the data used to create the mix can be saved  to
an  ascii script file by selecting _S_a_v_e _r_t _s_c_r_i_p_t or _S_a_v_e _r_t
_s_c_r_i_p_t _A_s under the _F_i_l_e menu.  Save the mix data frequently
so that you can revert to the most recently saved version if
you botch things up.  We recommend that you save these files
-  like  other  _a_s_c_i_i  files  - in your current working Unix
(rather than _s_n_d)  directory,  and  include  the  file  name
extension  ._r_t  (such as _m_i_x_1._r_t), so that _r_t will recognize
these files in the future.  These ascii files can be  viewed
with  a  utility  such as _c_a_t, or even edited with _v_i (which
advanced users sometimes find more  efficient  than  editing
within _r_t itself).
                    -  -  -  -  -  -  -

Three local Eastman scripts, called _r_t_l_e_a_r_n, _r_t_t_e_m_p_l_a_t_e  and
_r_t_o_p_e_n,  may  help  you  get started using _r_t. Separate _h_e_l_p
files are available on each of these utilities.

                     February 10, 1997
