diff --git a/db/manifest b/db/manifest
index 22a6bfa7d..2600c5981 100755
--- a/db/manifest
+++ b/db/manifest
@@ -173,3 +173,4 @@ scheduled_sessions_next_session_scheduled.sql
 fix_users_location_fields.sql
 audio_latency.sql
 ams_index.sql
+update_ams_index.sql
diff --git a/db/up/update_ams_index.sql b/db/up/update_ams_index.sql
new file mode 100644
index 000000000..b2bb4b92d
--- /dev/null
+++ b/db/up/update_ams_index.sql
@@ -0,0 +1,55 @@
+CREATE OR REPLACE FUNCTION ams_index (my_user_id VARCHAR, my_locidispid BIGINT, my_audio_latency INTEGER) RETURNS VOID STRICT VOLATILE AS $$
+  BEGIN
+    -- output table to hold tagged music sessions with latency
+    CREATE TEMPORARY TABLE ams_music_session_tmp (music_session_id VARCHAR(64) NOT NULL, tag INTEGER, latency INTEGER) ON COMMIT DROP;
+
+    -- populate ams_music_session_tmp as all music sessions
+    INSERT INTO ams_music_session_tmp SELECT DISTINCT id, NULL::INTEGER AS tag, NULL::INTEGER AS latency
+      FROM active_music_sessions;
+
+    -- TODO worry about active music session where my_user_id is the creator?
+    -- eh, maybe, but if the music session is active and you're the creator wouldn't you already be in it?
+    -- so maybe you're on another computer, so why care? plus seth is talking about auto rsvp'ing the session
+    -- for you, so maybe not a problem.
+
+    -- tag accepted rsvp as 1
+    UPDATE ams_music_session_tmp q SET tag = 1 FROM rsvp_slots s, rsvp_requests_rsvp_slots rrs, rsvp_requests r WHERE
+      q.music_session_id = s.music_session_id AND
+      s.id = rrs.rsvp_slot_id AND
+      rrs.rsvp_request_id = r.id AND
+      r.user_id = my_user_id AND
+      rrs.chosen = TRUE AND
+      q.tag is NULL;
+
+    -- tag invitation as 2
+    UPDATE ams_music_session_tmp q SET tag = 2 FROM invitations i WHERE
+      q.music_session_id = i.music_session_id AND
+      i.receiver_id = my_user_id AND
+      q.tag IS NULL;
+
+    -- musician access as 3
+    UPDATE ams_music_session_tmp q SET tag = 3 FROM music_sessions m WHERE
+      q.music_session_id = m.id AND
+      m.musician_access = TRUE AND
+      q.tag IS NULL;
+
+    -- delete anything not tagged
+    DELETE FROM ams_music_session_tmp WHERE tag IS NULL;
+
+    -- output table to hold users involved in the ams_music_session_tmp sessions and their latency
+    CREATE TEMPORARY TABLE ams_users_tmp (music_session_id VARCHAR(64) NOT NULL, user_id VARCHAR(64) NOT NULL, latency INTEGER) ON COMMIT DROP;
+
+    -- populate ams_users_tmp as all musicians in the ams_music_session_tmp sessions with full latency and music session
+    INSERT INTO ams_users_tmp SELECT c.music_session_id, c.user_id, (s.score+my_audio_latency+c.last_jam_audio_latency)/2 AS latency
+      FROM ams_music_session_tmp q
+      INNER JOIN connections c ON c.music_session_id = q.music_session_id
+      LEFT OUTER JOIN current_scores s ON s.alocidispid = c.locidispid
+      WHERE s.blocidispid = my_locidispid;
+
+    -- calculate the average latency
+    UPDATE ams_music_session_tmp q SET latency = (select AVG(u.latency) FROM ams_users_tmp u WHERE
+      q.music_session_id = u.music_session_id);
+
+    RETURN;
+  END;
+$$ LANGUAGE plpgsql;
diff --git a/ruby/spec/jam_ruby/models/active_music_session_spec.rb b/ruby/spec/jam_ruby/models/active_music_session_spec.rb
index effc53291..05fc301d7 100644
--- a/ruby/spec/jam_ruby/models/active_music_session_spec.rb
+++ b/ruby/spec/jam_ruby/models/active_music_session_spec.rb
@@ -385,10 +385,39 @@ describe ActiveMusicSession do
     end
 
     # todo we need more tests:
-    # rsvp'd user (chosen and not chosen)
-    # invited user
-    # creator (who should be automatically rsvp'd)
-    # musician_access and not
+    #
+    # the easiest collection of tests, not involving filtering, just tagging and latency, still result in many cases
+    # (given a creator, member, and observer):
+    #
+    # {not_rsvp, rsvp_not_chosen, rsvp_chosen} x
+    # {not_invited, invited} x
+    # {no_musicians, musicians_on_approval, musicians_freely_join} x
+    # {creator_not_member, creator_is_member} x
+    # {observer_not_member, observer_is_member} x
+    # {observer_member_not_scored, observer_member_scored}
+    #
+    # eh, that's 144 cases all told, and that doesn't cover the cases with multiple members...
+    #
+    # member is the user in the session
+    # creator is the user that created the session
+    # observer is the user making the call to ams_index
+    #
+    # the first two categories (rsvp and invited) are about the observer.
+    #
+    # i see this being written like this:
+    #
+    # test_ams([:not_rsvp, :not_invited, :no_musicians, :creator_not_member, :observer_not_member, :observer_member_not_scored],
+    #   member_latency, observer_member_score, observer_latency, expected_count, expected_tag, expected_latency)
+    #
+    # ... repeat as above with all the various combinations by choosing one from each category and appropriate other
+    # values and then expected results ...
+    #
+    # expected_count is 0 for the above written case, and would be 1 in the cases where any of rsvp_chosen, invited,
+    # musicians_on_approval, or musicians_freely_join are specified. test_ams would know which session and user should
+    # appear in the results of ams_index and ams_users.
+    #
+    # there should be an additional active music session created and joined by a distinct user, other. it should never
+    # appear in results.
   end