The SA-1 is a Pulse Code Modulation (PCM) monophonic 2note polyponic mini-keyboard which runs off 6volts or 4 AA batteries. There are 100 tones (TONE BANK) 19 rhythms on the white keys and 13 backings on the black keys and one demo tune.
This is not a sophisticated instrument and yet is surprisingly well-equipped in the sound department - the PCM tones being crystal clear and all but a few being useable - in fact some of them knock spots off some other higher range models I have heard,as in places there is in built echo and reverb effects. The tones are selected via the 10 numeric keys -so tone 55 is selected by pressing 5 twice. The backings and rhythms are selected by pressing the select button and then pressing a black or white key. The backings and rhythms are what you would expect from something this tiny - a tin box orchestra - not for the serious musician!
With some of the tones there is split and layering - allowing two tones to be played simltaneously or on two separate areas of the keyboard.The volume is digitally selected using and up an down button and the whole sound can be taken to headphones,which is probably better than using the external connection as a LINE OUT for recording as it is very noisy.
Good points: A 100 PCM sounds on something so cheap has to be a selling point and is pretty much the ONLY selling point of the SA-1. As an instant source of PCM samples it adds spice to an SK-1 or SK-5!
Niggles: 2 note polyphony is pretty much a waste of time unless you plan either sampling the PCM tones or using the SA-1 as a melody instrument. The rhythm unit is pointless and the digital volume annoyingly triggers a noise so there is no way to record the SA-1 and adjust the volume without ruining your recording. The added hiss on the output means it is pretty much useless for recording anyway - unless you have a sampler that can clean up the sample.You also need child's fingers to play the keys ,so unless you just want something to carry around that makes more noises than a VL-1 to work on those songs whilst in transit - one wonders why Casio just didn't put all those sounds on a better keyboard,but then in making music available to everyone - even your offspring can start early on this one!