http://noname.c64.org/csdb/release/?id=72678&show=notes
Its worthy to mention only because such a method is (unfortunately) not possible on the Oric's AY

It is possible to produce higher resolution samples on the Oric but this is through combining 2 or 3 channels together. The maximum is almost 8 bit resolution.
The AY can only generate square waves and even the Envelopes Sawtooth and triangle waveforms are based on 4bit.