[music-dsp] Costello Reverb...

[fintain conway]

I am trying to implement a version of Sean Costellos reverb, but at the 
moment it doesn't
sound very good. I'll do a quick walk through of what I am doing,
if there is an obvious mistake please highlight.

Start with 8 circular buffers of 4096 sample.
The operation on each buffer is the same:
A write pointer circles the line. To read a sample, I take the delay time 
for a given buffer, as given in the
paper (prime numbers 4127,2143,1933...) and modulation it with low frequency 
noise.
This is done sampling a noise source at a given frequency,and then linearly 
intepolating to this new value over a number of cycles
to smooth the delay time change. Kind of like a smoothed sample and hold.
I then use this post modulation delay time to do a fractional index into the 
given circular buffer using linear interpolation.
This is the reverb output for a single delay line.
I then take the write pointer and put in the current audio input sample 
along with feedback taken from the buffer at the
pre-modulation with noise point (4127..). Before adding the feedback, it is 
first low pass filtered (damping) and subtracted from a scatter
junction coeff, which is based on an average of all the delay lines low pass 
filter memeory.

Any glaring errors? If need can post some code, but its abit more ugly, even 
than this post.

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