Call macOS's "say" program with every possible voice at the same time with the given phrase.

say.js

#!/usr/bin/env node

/**
 * Call macOS's `say` program with every possible voice at the same
 * time with the given phrase. Scare your pets.
 */

const { exec } = require('child_process');

function getVoices(callback) {
  const command = 'say -v ?';
  console.log('attempting to list the available voices');
  return new Promise((resolve, reject) => {
    console.log('starting the say process with %s', command);
    exec(command, (err, stdout, stderr) => {
      if (err) {
        reject(err);
        return;
      }
      stdout = stdout.toString('utf8');
      const lines = stdout.split('\n');
      const voices = lines.map(l => l.split(' ')[0])
      resolve(voices);
    });
  })
}

function saySomething(phrase, voice) {
  const command = `say -v ${voice} ${phrase}`;
  console.log('executing command "%s', command);
  return new Promise((resolve, reject) => {
    exec(command).on('exit', (code, signal) => {
      console.log('%s exiting', voice);
      resolve();
    });
  });
}

function parseArgs() {
  const args = process.argv.slice(2);

  if (args.length === 0) {
    console.log('Please specify something to say!');
    process.exit(1);
  }

  let synchronous = false;
  if (['-s', '--synchronous'].includes(args[0])) {
    synchronous = true;
    args.splice(0, 1);
  }

  const phrase = args.join(' ');

  return { phrase, synchronous };
}

async function main() {
  const { phrase, synchronous } = parseArgs();
  const voices = await getVoices();
  if (synchronous) {
    for (const voice of voices) {
      await saySomething(phrase, voice);
    }
  } else {
    voices.forEach(voice => saySomething(phrase, voice));
  }
}

main();