nBurnFPS is the frames per second, for 60hz it would be 6000, for 58.97 it would be 5897
find all occurences of chip->sample_rate = in the register writes, and change to:
			chip->sample_rate = chip->master_clock / (16 * (chip->active_voices + 1));

#define BURN_SND_CLIP(A) ((A) < -0x8000 ? -0x8000 : (A) > 0x7fff ? 0x7fff : (A))

void ES5506Update(INT16 *pBuffer, INT32 samples)
{
	INT32 *lsrc = chip->scratch, *rsrc = chip->scratch;

#if MAKE_WAVS
	/* start the logging once we have a sample rate */
	if (chip->sample_rate)
	{
		if (!chip->wavraw)
			chip->wavraw = wav_open("raw.wav", chip->sample_rate, 2);
	}
#endif

	INT32 rate = (chip->sample_rate * 100) / nBurnFPS;
	samples = rate;

	/* loop until all samples are output */
	while (samples)
	{
		INT32 length = (samples > MAX_SAMPLE_CHUNK) ? MAX_SAMPLE_CHUNK : samples;
		INT32 samp;

		/* determine left/right source data */
		lsrc = chip->scratch;
		rsrc = chip->scratch + length;
		generate_samples(lsrc, rsrc, length);

		/* copy the data */
		INT32 len = (length * samples) / rate;

		for (samp = 0; samp < len; samp++)
		{
			INT32 k = (samp * rate) / samples;

			pBuffer[0] = BURN_SND_CLIP((INT32)((lsrc[k] >> 4) * chip->volume[0]));
			pBuffer[1] = BURN_SND_CLIP((INT32)((rsrc[k] >> 4) * chip->volume[1]));
			pBuffer += 2;
		}

#if MAKE_WAVS
		/* log the raw data */
		if (chip->wavraw)
			wav_add_data_32lr(chip->wavraw, lsrc, rsrc, length, 4);
#endif

		/* account for these samples */
		samples -= length;
	}
}