Ethan has released his PSPSeq. PSPSeq is a port of the basic synthesis environment he wrote for the ADSP-218x, a 16-bit digital signal processor, with a simple UI. Details from the readme:

usage of PSPSeq

when none of the action buttons (x, o, square, triangle) are pressed, the
directional keys are used to move either one step left/right, or up/down one
track. pushing the analog stick to the left or right moves the active
step to either step 0, 8, 16, or 24; whichever is closer in whatever direction
the stick is moved.

when x is pressed, this enables the trigger and volume functionality. moving
the analog stick up/down increases and decreases the likelyhood that this track
will retrigger. a trig of 100 means that this track will always retrigger when
the sequencer reaches that hit, while a trig of 50 means there is a 50% chance
of a retrigger and a 50% chance of the hit not occuring. moving the analog
stick left/right decreases or increases the volume of this particular hit.

when triangle is pressed, this enables configuration of a single parameter for
the hit and the left/right panning of the track. moving the analog stick to
the left/right controls the panning on the track. note that panning is a global
parameter; all hits on a track have the same pan value. moving the analog stick
up/down controls the unqiue parameter value for each track. these parameters
are customizable for each hit on a track.

if a track already has one trigger point in it and the current selected step has
never had any trigger/volume data written to it, it will assume the
characteristics of the previous initialization in this track.

pressing the o button controls the tempo of the loop. moving the analog stick
to the right slows the tempo while moving it to the left increases the tempo.

installation of PSPSeq

the zip file PSPSeq000.zip contains two main subdirectories; 1.0 and 1.5. if
you are using firmware 1.0 copy EBOOT.PBP from this directory onto your memory
stick and execute it like you would any other PBP file. for firmware revision
1.5, copy the PSPSEQ and PSPSEQ% directories to the /PSP/GAME/ directory on
your memory stick.

History

PSPSeq0.00 jan 28 2006

first teaser release of PSPSeq. most basic sequencing functionality is
implemented but none of the song or sound design functionality is in place.
many new features to be added soon!

Download: [PSPSeq 0.00]