diff --git a/lib/synth-audio.js b/lib/synth-audio.js
index 60aae1a..32b3d31 100644
--- a/lib/synth-audio.js
+++ b/lib/synth-audio.js
@@ -53,6 +53,8 @@ const EXPIRES = JAMBONES_TTS_CACHE_DURATION_MINS;
 const OpenAI = require('openai');
 const getAwsAuthToken = require('./get-aws-sts-token');
 
+/* counter for playback id */
+let playbackIdCounter = 0;
 
 const trimTrailingSilence = (buffer) => {
   assert.ok(buffer instanceof Buffer, 'trimTrailingSilence - argument is not a Buffer');
@@ -589,8 +591,8 @@ const synthMicrosoft = async(logger, {
     }
     if (!JAMBONES_DISABLE_TTS_STREAMING && !JAMBONES_DISABLE_AZURE_TTS_STREAMING &&
       !renderForCaching && !disableTtsStreaming) {
-      let params = '';
-      params += `{api_key=${apiKey}`;
+      let params = '{';
+      params += `api_key=${apiKey}`;
       params += `,language=${language}`;
       params += ',vendor=microsoft';
       params += `,voice=${voice}`;
@@ -853,8 +855,9 @@ const synthElevenlabs = async(logger, {
 
   /* default to using the streaming interface, unless disabled by env var OR we want just a cache file */
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += ',vendor=elevenlabs';
     params += `,voice=${voice}`;
     params += `,model_id=${model_id}`;
@@ -943,8 +946,9 @@ const synthPlayHT = async(client, logger, {
 
   /* default to using the streaming interface, unless disabled by env var OR we want just a cache file */
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += `,user_id=${user_id}`;
     params += ',vendor=playht';
     params += `,voice=${voice}`;
@@ -1010,8 +1014,9 @@ const synthInworld = async(logger, {
 
   /* default to using the streaming interface, unless disabled by env var OR we want just a cache file */
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += `,model_id=${model_id}`;
     params += ',vendor=inworld';
     params += `,voice=${voice}`;
@@ -1074,8 +1079,9 @@ const synthRimelabs = async(logger, {
 
   /* default to using the streaming interface, unless disabled by env var OR we want just a cache file */
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += `,model_id=${model_id}`;
     params += ',vendor=rimelabs';
     params += `,language=${language}`;
@@ -1130,8 +1136,9 @@ const synthVerbio = async(client, logger, {credentials, stats, voice, text, rend
   }
   const token = await getVerbioAccessToken(client, logger, credentials);
   if (!process.env.JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{access_token=${token.access_token}`;
+    let params = '{';
+    params += `access_token=${token.access_token}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += ',vendor=verbio';
     params += `,voice=${voice}`;
     params += ',write_cache_file=1';
@@ -1173,8 +1180,9 @@ const synthWhisper = async(logger, {credentials, stats, voice, text, instruction
   const {api_key, model_id, baseURL, timeout, speed} = credentials;
   /* if the env is set to stream then bag out, unless we are specifically rendering to generate a cache file */
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += `,model_id=${model_id}`;
     params += ',vendor=whisper';
     params += `,voice=${voice}`;
@@ -1219,8 +1227,9 @@ const synthWhisper = async(logger, {credentials, stats, voice, text, instruction
 const synthDeepgram = async(logger, {credentials, stats, model, text, renderForCaching, disableTtsStreaming}) => {
   const {api_key, deepgram_tts_uri} = credentials;
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += ',vendor=deepgram';
     params += `,voice=${model}`;
     params += ',write_cache_file=1';
@@ -1262,8 +1271,9 @@ const synthCartesia = async(logger, {
   const opts = !!options && Object.keys(options).length !== 0 ? options : JSON.parse(credOpts || '{}');
 
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += `,model_id=${model_id}`;
     params += ',vendor=cartesia';
     params += `,voice=${voice}`;
@@ -1333,8 +1343,9 @@ const synthResemble = async(logger, {
 
   /* default to using the streaming interface, unless disabled by env var OR we want just a cache file */
   if (!JAMBONES_DISABLE_TTS_STREAMING && !renderForCaching && !disableTtsStreaming) {
-    let params = '';
-    params += `{api_key=${api_key}`;
+    let params = '{';
+    params += `api_key=${api_key}`;
+    params += `,playback_id=${playbackIdCounter++}`;
     params += ',vendor=resemble';
     params += `,voice=${voice}`;
     params += ',write_cache_file=1';