How do you program sound blasters?

The Sound Blaster Pro (May 1991) was the first significant redesign of the card's core features: It could record and play back digitized sound at faster sampling rates (recording up to 22 kHz, playback up to 45 kHz), could do so in stereo (up to 22 kHz), and added a "mixer" which allowed independent volume control of the various subsystems on the card as well as enable a crude highpass or lowpass filter. The first version of the Pro also used two YM3812 chips (one for left audio channel and the other one for the right one; both chips had to be programmed identically to get mono sound if not using the AdLib compatible interface). Version 2.0 switched to the improved Yamaha YMF262 chip, also known as OPL3. MIDI support became full-duplex and offered time stamping features, but was not yet industry-standard MPU-401 compatible.